Tech Talk

Attention : C5 owners and potential owners. I've received numerous calls from people after information to help determine a cars mechanical / electrical fault history. I have put together this section so you can check on a vehicles past or present faults through it's on board diagnostics system. I have found this very useful with my own C5!!!!

C5 Corvette ---- Dashboard Diagnostics c5_diagnostic_display

The 1990's in America saw the Feds buckle down requiring all cars and light commercials sold after Jan.1 1996, be equipped with an onboard diagnostic system including an "Assembly Line Diagnostic Link," which is used to retrieve powertrain information with a scan tool. To ease the diagnostic process, regulations dictate that the ALDL must be located within 3 feet of the driver and that it does not require any tools to be accessed. When the system detects a powertrain problem, it logs it as a fault code in the vehicles computer memory. When retrieved, this code provides information regarding the source of the problem. A "check engine" or "maintenance required" light illuminates and being able to quickly retrieve and interpret the fault code behind that "check engine" light could get you back on the road in a few minutes or even save your engine.

The Instrument Panel Cluster (IPC) has the ability to display diagnostic trouble codes (DTCs) from the various modules that transmit them. For C5's built before 15/12/97, there are 48 different DTC's; later C5's equipped with the Active Handling Option have a few more. A full list of these DTC's can be found in your car's service manual.

You can enter the Diagnostic Display mode by using the following procedure:

  1. Turn the ignition to the "On" position but don't start the engine.
  2. Press the "Reset" button on the Driver Information Centre (DIC) to turn off any existing warning messages.
  3. Press and hold the "Options" button
  4. While holding the "Options" button, press the "Fuel" button four times within a 10- second period.

The onboard diagnostics system will go into the "Automatic" mode, which shows each module's DTCs in a preset sequence:

  1. 10 - PCM ( Powertrain Control Module)
  2. 28 - TCS ( Traction Control System ) commonly known as the yellow button !!!!
  3. 38 - RTD ( Real Time Damping. Some models don't have this option )
  4. 40 - BCM ( Body Control Module )
  5. 60 - IPC ( Instrument Panel Cluster )
  6. 80 - Radio
  7. 99 - HVAC ( Heater Vent-Air Conditioning )
  8. AO - LDCM ( Left Door Control Module )
  9. A1 - RDCM ( Right Door Control Module )
  10. AC - SCM ( Seat Control Module )
  11. BO - RFA ( Remote Function Actuation )

For each module, all existing DTC's will be displayed. If no faults are present in a particular module, you'll see " No More Codes " on the IPC display.

There are two kinds of DTC's. The first is a " Current " code, which is designated with a letter suffix " C." A current code indicates a malfunction is present at this time. The second is a " History " code, which is designated with a letter suffix " H." A History code indicates that a malfunction was present at some time in the past 40 to 50 ignition cycles. A history code could indicate the presence of an intermittent fault.

If you want to erase the DTC's in a given module, press and hold the " Reset " button until the display reads " No More Codes." Keep in mind that clearing a trouble code doesn't repair the underlying problem

Now that you've retrieved your C5's DTC's, the next step is to narrow down the possible causes. If you're a DIY'er, you may wish to purchase a scan tool capable of performing more-in-depth diagnostics but here in Queensland we use Performax International at Gympie. They have the right tools and expertise to solve any of these issues. While we don't have room here to list all the C5 DTC's, you can find them at

Additionally talk to club member Dave Kelly, I've heard him recite all the codes out of his head, I think he has a built in scan tool !!!!

I hope this may help some of you, with 7 computers on board the C5 is more than a car, and if things aren't right the car will tell you to fix it....

Cheers, Peter Turner

April 25,2004
Revised October 26, 2005
1963-1979 Corvette Differential Rebuild Procedure
By Gary Ramadei

Tools Required

  • Dial inch - pound torque wrench, 0-30 range- It's important to use this type of wrench for accuracy
  • Torque wrench- 0-150 ft/lbs. I prefer the click typediff
  • 1" dial indicator with magnetic base
  • 0-1" micrometer and / or 0-6" dial caliper
  • Impact wrench
  • Bearing splitter
  • 20 ton press
  • Brass drifts
  • Hammers
  • Basic hand tools
  • 2-jaw gear puller
  • ¼ " NPT tap
  • 90* snap ring pliers

Starting Procedure

  1. Remove differential from car
  2. Clean off dirt/oil, grease before opening
  3. Remove rear cover and drain old oil into container
  4. Check old oil for metal particles using a magnet
  5. For ease in disassembly, mount the differential to an engine stand by using the 3/8-16 tapped holes for the strut rod bracket.
  6. If the same ring and pinion is going to be re-used check the backlash and pattern before removing or disturbing bearings, pinion or carrier. Make note of backlash and pattern for future reference.
  7. Stamp the carrier bearing caps - Right & Left so they can be put back on their original sides. They are machined per side.
  8. Remove Pinion yoke nut
  9. Remove carrier bearing caps & bolts. Note the bolt head markings. 6 line minimum required (grade 8).
  10. Use a box wrench on one of the ring gear bolts and rotate the pinion to move the carrier out of the housing. The carrier bearing shims are preloaded and will require some force to remove the carrier.
  11. Keep the carrier bearing shims together per side. Place them with the respective bearing cap.
  12. Clean the carrier in solvent to remove oil.
  13. Use an old side yoke and side yoke bearings mounted in a bench vise to hold the carrier assembly.
  14. Use a brass drift to drive the old pinion out. Hold the pinion face so it doesn't crash to the floor or make up a plate to bolt to the bearing cap holes to catch the pinion while driving out.
  15. Clean parts in solvent.

Disassembly for Inspection

  1. After cleaning housing, drive out old pinion bearing races.
  2. Drive out old side yoke needle bearings, Torrington #BH2212
  3. Chase the bearing cap holes with a 7/16-14 tap.
  4. Use a file to radius the housing edges to remove any burrs or sharp edge.
  5. Optional but recommended. Drill and tap a drain hole for ¼" NPT. Locate at 1" from the edge of the strut rod bracket pad. Use of a magnetic plug is recommended. CAUTION: tapping a NPT plug requires you not to fully tap the hole. Continue to check the fit of the plug in the hole and stop when you have ½ the tapered thread screwed in. Over tapping the hole will result in a leak. Use Permatex high temp thread sealant on the plug threads when installed.
  6. Check housing for any damage, cracks, etc. Note the side yoke holes to see if the yokes were worn to the point of grinding into the housing.
  7. Remove the ring gear bolts from the gear/carrier. These should be tight, some of the later 70's differentials had a problem with loose ring gear bolts.
  8. Using a mallet tap off the ring gear. Check for wear, chip teeth, cracks, etc.
  9. If reusing the ring gear, stone down the backside where the bolt-holes are to remove any burrs/high spots. I recommend using new gears in most cases, the initial added cost may seem high but setting up unknown used gears or worn gears can be a hassle.
  10. If using new gears, follow the same procedure for cleaning/deburring.
  11. Mount carrier back on old side yoke in the bench vise so you can remove the posi clutches.
  12. Use channel locks, bolt or tie together the posi springs. These are under pressure so be careful they don't fly out.
  13. Remove the 7/16 hex head pinion gear "pin" bolt from the carrier, retain the star washer.
  14. Slide out the pinion gear shaft or "pin" from the carrier.
  15. Remove the posi spring plates.
  16. Rotate the carrier on the yoke until one pinion gear and cup washer is in the large "window" and can be removed.
  17. Rotate the carrier until the other pinion gear and cup washer can be removed. The upper side gear in the carrier will have to be supported by hand as the carrier is rotated to prevent it from falling down into the carrier.
  18. With the pinion gears removed, remove the side gears, posi clutches, side gear shims, and clutch retainers.
  19. Clean the parts again and keep the clutches with each side together.
  20. Use a 2-jaw puller and remove the carrier bearing cones. A spacer the diameter of the carrier boss will be needed to press against when using the puller.Note: the boss is slightly higher then the bearing ID race. It is important the bearing ID race is fully seated against the shoulder of the carrier when installing new bearing cones.
  21. Inspect the type of posi clutch and the condition. There are several types of clutches. Eaton used solid steel and "snowflake" steel clutches. The "snowflake" clutches are slotted to get oil in between the clutches to eliminate chatter when they are hot and the car is cornering. They didn't work too well. Eaton now sells carbon fiber clutches also. However, I was told they don't hold up to extreme usage. Regardless, I use the solid steel clutches still available from any Eaton dealer.
  22. Inspect the clutch surface. They should have a solid diamond pattern to them. If they are shiny and the pattern is worn replace them. The new thickness of clutches is .068"-. 069" anything thinner then .067" I would replace the set. Most shops replace the clutch set as a normal rebuild procedure. The cost of a new set is about $100. It's not worth the trouble of having to remove the differential to replace them a short time later.
  23. Optional, but Highly recommended: Polish the carrier housing once it is clean and stripped of parts. Radius the edges of all the non-machined surfaces. This removes high spots that could lead to cracks in the casting. I place the carrier in a lathe and polish it with 240 grit and then 400-grit emery cloth. A die grinder or Dremel tool with stone or rotary bit will radius the edges, but don't cut deep into the carrier, just round off the edges smooth.
  24. Check for cracks from the window openings to the center pinhole. Check the pin hole for a step or egg shape. If worn badly then boring out a plug to the original dimension or bushing it can repair the carrier. Finding a good machine shop to align the bore may be a problem in some areas. Used Eaton carriers are now hard to find, you may have to buy a new loaded carrier. The pin should slide in the holes without any resistance but not be sloppy.
  25. With respect to the new Eaton carriers, part number 19670-010 they come loaded with fiber clutches. Again I have never used these so I can't offer an opinion on life or torque range. One friend who used them had a problem with chatter, but I don't know who set them up so it could have been another issue related to them? I use only the solid steel Eaton clutches in my cars.
  26. Inspect the carrier posi gears. There are a couple of different types depending on the year of the car. Count the number of teeth of both the side gear and pinion gear. They will be 10/16, 10/17, or 10/18. The 10/17's are the best and strongest. Treated 10/17 sets are available for HD.
  27. The gears are ok to re-use as long as there is no damage to them.
  28. If you are following the GM posi procedure, the side gear backlash will need to be measured. Shims are used behind the side gear to obtain the specified backlash per side. Once the backlash is correct the 4 springs can be installed. Follow the procedure in a GM overhaul manual to fully understand. I do not use this procedure. Instead I "tune" the posi.
  29. Using a die grinder or Dremel tool, radius the edges of the side gear and pinion teeth. Just apply minor pressure to round off the edge not cut into the tooth.
  30. OptionalPosi Tuning Procedure: purchase a shim kit. Start out using .045" shim behind each side gear. Assemble the carrier without the 4 posi springs or plates. Gather the posi clutches you will be using. Look at the edges of the clutches and you should see where the stamping was done and the grooves are deeper on one side. Sometimes a magnifying glass helps determine the side. Alternate stacking the clutches by the groove depth-deep side against shallow side, deep side, shallow side, etc. The clutches with tabs go in between the solid clutches and follows the same pattern with the grooves. Lube the clutch surfaces with GM posi additive as you assemble them. Use the retainers to hold the clutches together while installing them into the carrier. With the carrier assembled rotate it on the side yoke in the vise. It may be loose or snug. Flip the carrier over and check the other side gear for feel. If the gears are too loose add shims in .005" increments until the teeth of the side gear and pinion gears start to bind. I use a large spanner wrench to rotate the carrier on the yoke. When the gears start to bind remove .005" shim from the side gear you are checking. I remove the shim and grind it on a surface grinder once I get to the point of gear bind. I remove .001" at a time until the gears just start to rotate without any binding. Once you get both sides to this point the carrier is ready for the ring gear.
  31. Rebuild kits come with new 7/16-20 bolts. However they are not the shouldered type of bolt the factory used. If you can find the original type use them. Another option is to use ARP #230-3001 ring gear bolts. They add about 430 to the job but are high quality bolts. Always install new bolts when installing the ring gear. Use red Loctite, #271 or #272 high temp, thread locker on the ring gear bolts. I cut the heads off the old bolts and slot them to use a screwdriver with. Screw a bolt into every other tapped hole in the ring gear. This will act as a guide to draw up the ring gear. Install the new bolts in the remaining open holes, using Loctite on them. I use an impact gun to slowly draw up the ring gear. You can also use a press but be careful not to damage the gear teeth. With the gear in place remove the screw in bolts and install the balance of new bolts again using the red Loctite. Torque in a star pattern to 55 ft/lbs.
  32. Install new carrier bearings. Be sure they are seated against the hub shoulder. A large socket can be used to support the ID race while pressing the bearing on.
  33. The carrier is now complete and read for installation in the housing. Put it aside until you are ready to use it.
  34. Remove the old pinion bearing from the pinion. A bearing splitter and press will be needed to remove the bearing.
  35. Save and note the shim size under the bearing. This shim will determine the pinion depth into the ring gear. It is vital to get the pinion centered on the ring gear during setup or gear noise or damage will result.
  36. Inspect the old pinion for wear or damage if reusing.
  37. Setup Note: I use an old good bearing that I polished the ID on so it will slip fit onto the pinion. This will save pressing the new bearing on/off several times and remove the risk of damaging it.
  38. Use the original shim or equivalent size in a new shim on the pinion to start.

Differential Assembly

  1. Install the new pinion bearing races in the housing. I use a seal/race tool made out of aluminum. A brass drift or steel plate will also work.
  2. Lightly oil the races with 90-wt-gear oil and install the pinion.
  3. Holding the pinion in place against the race, install the yoke, washer, and original nut. Note: Do not use the new nut, seal, or crush sleeve at this time.
  4. Tighten the nut until the bearings seat and removes end play. Using a dial in/lb. torque wrench with 0-30in/lb rating tighten the nut until there is 15-17 inch/lbs. of rotational drag on the bearings. This will preload them in the final position. A very slight tap with a brass hammer or drift against the pinion ends will help seat the bearings. Remember very light tap!
  5. Install the carrier in the housing. Rotate the pinion by hand to be sure they move freely.
  6. Using new shims add approximately the same size per side as the original cast shims were. Do not use the original cast shims. You may have to decrease the shim size to start.
  7. The carrier should drop in with just a little resistance. It should be able to be removed by hand.
  8. Install the bearing caps and torque to 60 ft/lbs. Do not use the bolts to draw down the caps, instead use a hammer to tap the caps in place then torque.
  9. With the caps torqued check the backlash in the ring gear. Use a 1" dial indicator and magnetic base to check the backlash. Backlash ranges from .006-. 010" depending on the gear manufacturer. Refer to your note on the original backlash if reusing the gears. I set new Tom's US Gears to between .007-. 009" and get a nice pattern.
  10. If the backlash is not where it should be then you have to adjust the carrier shims in or out. If the backlash is too tight then the ring gear has to move away from the pinion. Remove .005 from the left shim and add .005 to the right shim as a starting point. If the backlash is too loose then the ring gear needs to go into the pinion.
  11. Once the backlash is correct you need to see where the pinion is n relation to the ring gear center. Use marking paste, either white or yellow, and paint the teeth-both sides, in 2 places. Paint several teeth in each area.
  12. Use a rag rolled up to act as a brake and load up the pinion gear while rotating it several revolutions in each direction. I use a 9/16" box wrench I made up. I took a 9/16-combo wrench and cut off the open-end side. I welded the wrench to a long piece of 5/8" Cold Roll Steel. Husky makes a nice double box wrench that works well too. A pattern will form in the marking grease. Look to see if the pattern is the same length in the base of the tooth and the top of the tooth. The convex side of the tooth is called the drive side, the concave side of the tooth is called the coast side. The end of the tooth near the center of the ring gear is called the Toe. The end of the tooth near the OD of the ring gear is called the Heel.
  13. The pinion shim must be adjusted to get the pattern centered on the tooth, regardless of where the pattern is in relation to the toe or heel. Once the pattern is centered, see where the pattern is for the toe and heel. Ideally they should be both centered on the tooth but this is not always possible. If the drive side is centered or to the toe that's ok. Under load it will spread out toward the heel. Performance setups are toward the Toe on the drive side. The coast side should be centered. With new gears and correct shim and backlash the pattern should be in this range. Refer to installation information that may come with the new gear set.
  14. It will take several tries to get the pattern in range, so don't give up.
  15. Decreasing Backlash moves the Drive side slightly lower and to the toe, the Coast moves lower and to the Toe.
  16. Increasing Backlash moves the Drive side slightly higher and to the Heel, the Coast moves higher and to the Heel.
  17. Thicker pinion shim with good Backlash moves the Drive side deeper and Slightly to the Toe. The coast moves deeper and more to the Heel.
  18. Thinner pinion shim with good Backlash moves the Drive side to the top and to the Heel. The Coast moves tot he top and Slightly to the Toe.
  19. Once the pinion shim, backlash, and pattern are correct then disassemble again.
  20. Install the new bearing if you have been using a setup slip fit bearing. Setup again to get the pattern right.
  21. With the correct pattern and new bearing installed, disassemble,
  22. This time the crush sleeve or solid pinion shim will be installed along with a new pinion seal and new nut.
  23. Oil the pinion bearing with 90 wt gear oil, install the pinion in the housing, install the crush sleeve and outer bearing, pinion seal, yoke, washer and new nut. Use Loctite red on the nut. Torque the nut to get your setup rotational drag. The trick here is the crushing of the sleeve. It will take a BIG impact gun, Long breaker bar, or some other device to start the crush. I have used two methods that work. The first one is to place the housing with the pinion, in a press and press against the pinion until the bearings seat. Then just a little bit more. Remove the housing and check it with the dial torque wrench. Once the sleeve begins to crush the impact gun will drive it down. You don't want to over crush the sleeve. If you over crush it then replace it with a new sleeve. The second method is to crush the sleeve in a press before installing it on the pinion. I measure the old sleeve to get a close reference point. Then install the sleeve in the press and use a plate against the OD. I press it until it starts to compress and begin the crush. I then install in on the pinion and use my impact gun to set it. Another method is to use a solid spacer and shims. This replaces crushing the sleeve, instead shims are used to set the length needed to preload the bearings and keep them from loosening up. I have not used the solid spacer yet but other have and report it is much faster and more accurate to set then the crush sleeve. The solid spacers can be made or purchased from Ratech in OH.
  24. NOTE: The pinion seal Flange does not bottom out against the housing when installing. There should be a 1/8"(.125") gap between the housing and the seal flange. Use Permatex #2 sealant on the pinion splines to prevent oil leaking past the nut, I also put a little #2 on the seal OD Evenly tap the seal into the housing. A plate or wood block covering the seal OD will work to drive it in place. Place a little grease on the seal ID to prevent any dry damage when installing the pinion.
  25. Install the carrier, only this time add .005 shim to each side to add a preload to the carrier bearings. You will have to hammer the shims in because of the increased thickness.
  26. Install the bearing caps and at this time I swap out the hex head bolts for 7/16-14 socket head caps screws. They are a littler stronger. Some of the earlier differentials used a 5 line bolt marking that would not be a grade 8 bolt. The socket head cap screws are rated higher then grade 8 and work without any problem.
  27. For HD applications a steel bearing cap and ½-13 bolts are used. This will require fitting of the cap and tapping the holes for the larger size bolts.
  28. Install new Torrington BH2212 bearings in the side yoke bores, these are full needle bearings. Some of the kits I used came with bearings with half the needles in them. I trashed them.
  29. Install new yoke seals. Some seals I've used are slightly larger OD and don't easily fit the bore. The CR seals that NAPA sells work very well if you find you need seals or the ones in the kit are NG.
  30. Grease the seal ID here too.
  31. Install the side yokes. I don't reuse side yokes. The originals were case hardened and ride up against the posi pin. The pin is harder and the yoke ends wear. Once the case hardening is gone they wear out quickly. It's best to replace the yokes during a rebuild. The exchange yokes sold are rebuilt using hardened tips to prevent wear and offer a very long life span.
  32. With the yokes n place install new snap rings in the groove on the end of the yoke. You will need 90* snap ring pliers to install the rings. If you rebuilt the posi like I do then the end of the yoke will be right on the pin or within a few thousands. I fit a .001-. 004" gap in between them for oil to slip in. If you followed the GM overhaul manual you may have more end play in the yokes because the clutches will not be shimmed as close as the springless method.
  33. Add two bottles of GM posi additive and 90-wt-gear oil.
  34. Use Permatex #2 on the rear cover gasket and install the rear cover. Torque the bolts to 50 ft/lbs. I use the HD Muskegon Brake rear covers. They have thicker mounting tabs to withstand more abuse then the stock cover can. Also, improper rear spring installation can break the stock cover mounting tab off or crack the cover.

Break-in procedure

  1. f using a new ring & pinion gear set, drive the car for 10-12 miles moderately. Stop and let the differential cool for 45-60 minutes. Do this several times.
  2. Drain the oil at 500 miles. Use new GM limited-slip additive and 90-wt oil.


I can supply you with all the parts in this procedure. I also make up POSI tuning kits with the solid steel clutches, new retainers, posi additive, full shim kit, pinion washers, and full instructions. Contact me at 203-776-2813 x139 days or 203-387-5374 evenings.


I do not use synthetic oils or special additives. I use only the GM Limited-Slip additive and GM or equivalent 90-wt gear oil. This procedure is the way I rebuild these differentials and is meant to be used as an educational tool for the corvette hobbyist. This procedure differs in some respect from the GM overhaul manual. I claim no responsibility for problems that may develop by individuals following this procedure. The end result of any mechanical repair lies in the hands of the mechanic performing the work. If you have any doubt of your skills or questions on this procedure, consider having a professional do the work.

wd40WD 40 - Stuff you might not know. The product began from a search for a rust preventative solvent and de-greaser to protect missile parts. WD-40 was created in 1953 by three technicians at the San-Diego Rocket Chemical Company

It's name comes from the project that was to find a "water displacement" compound. They were successful with the fortieth formulation, thus WD-40.

The Corvair Company bought it in bulk to protect their Atlas missile parts. The workers were so pleased with the product, they began smuggling (also known as "shrinkage" or "stealing") it out to use at home. The executives decided there might be a consumer market for it and put it in aerosol cans. The rest, as they say, is history.

It is a carefully guarded recipe known only to four people. Only one of them is the "brew master." There are about 2.5 million gallons of the stuff manufactured each year. It gets it's distinctive smell from a fragrance that is added to the brew. Ken East says there is nothing in WD-40 that would hurt you.e:

Here are some of the uses:

  • Protects silver from tarnishing
  • Cleans and lubricates guitar strings
  • Gets oil spots off concrete driveways
  • Gives floors that 'just-waxed' sheen without making it slippery
  • Keeps flies off cows
  • Restores and cleans chalkboard’s
  • Removes lipstick stains
  • Loosens stubborn zippers
  • Untangles jewellery chains
  • Removes stains from stainless steel sinks
  • Removes dirt and grime from the barbecue grill
  • Keeps ceramic/terra cotta garden pots from oxidising
  • Removes tomato stains from clothing
  • Keeps glass shower doors free of water spots
  • Camouflages scratches in ceramic and marble floors
  • Keeps scissors working smoothly
  • Lubricates noisy door hinges on vehicles and doors in homes
  • Gives a children's play gym slide a shine for a super fast slide
  • Lubricates gear shift and mower deck lever for ease of handling on riding mowers
  • Rids rocking chairs and swings of squeaky noises
  • Lubricates tracks in sticking home windows and makes them easier to open
  • Spraying an umbrella stem makes it easier to open and close
  • Restores and cleans padded leather dashboards in vehicles, as well as vinyl bumpers
  • Restores and cleans roof racks on vehicles
  • Lubricates and stops squeaks in electric fans
  • Lubricates wheel sprockets on tricycles, wagons and bicycles for easy handling
  • Lubricates fan belts on washers and dryers and keeps them running smoothly
  • Keeps rust from forming on saws and saw blades, and other tools
  • Removes splattered grease on stove
  • Keeps bathroom mirror from fogging
  • Lubricates prosthetic limbs
  • Keeps pigeons off the balcony (they hate the smell)
  • Removes all traces of duct tape
  • I have even heard of folks spraying it on their arms, hands, knees, etc., to relieve arthritis pain.
  • One fellow claims spraying it on fishing lures attracts fish.

An Engineer Rambles

absRecently my 1990 Corvette began displaying a “Service ABS” light on the DIC (Driver Information Centre). That is the panel just above the radio, which displays various messages in red or yellow lights.

By now all C4 Corvette owners would be aware of the standard diagnostic routine to adopt when an error light appears.. Bend up a paper clip and use it to ground the terminal on the ALDL connector. In this instance, one uses the “H” terminal, which is the ABS (Anti-Lock Brake System) diagnostic. If you don’t know what I am talking about, you have not been paying attention and you need to re-read my earlier articles.

The result of my test was a Code 76, which means “Lateral Accelerometer fault - signal out of range or incorrect”. “”What is a lateral accelerometer?” I hear someone in the back row asking.

The ABS consists of the following elements

  • Modulator Valve and relays. Located under the left rear storage compartment
  • Control Module. The box full of electrical circuits. Also in storage compartment
  • Lateral Accelerometer. Located behind the instrument pane, under the radio.
  • Wheel Sensors and toothed rings. One at each wheel.
  • Wiring harness and module relay.
  • Fuse
  • Anti-lock Warning Lamp
  • Recently my 1990 Corvette began displaying a “Service ABS” light on the DIC (Driver Information Centre). That is the panel just above the radio, which displays various messages in red or yellow lights.

By now all C4 Corvette owners would be aware of the standard diagnostic routine to adopt when an error light appears. Bend up a paper clip and use it to ground the terminal on the ALDL connector. In this instance, one uses the “H” terminal, which is the ABS (Anti-Lock Brake System) diagnostic. If you don’t know what I am talking about, you have not been paying attention and you need to re-read my earlier articles.

The result of my test was a Code 76, which means “Lateral Accelerometer fault - signal out of range or incorrect”. “”What is a lateral accelerometer?” I hear someone in the back row asking.

The ABS functions by monitoring the speed of each wheel using the toothed rings and sensors. Basically the electronic control module takes as input, the frequencies of pulses generated as each tooth passes by its stationary inductive sensor. In the case of the Corvette system, the two rear wheels are treated as a pair, taking the lower wheel speed of the two rear wheels as the input for processing. This is known as a three channel system. In addition, the lateral accelerometer provides an output voltage proportional to the vehicle’s lateral acceleration.

The control module uses the information gathered from the wheel sensors and the lateral accelerometer to control the braking action of the wheels to prevent wheel lock. When the control module see that a wheel is about to lock (ie it is turning slower than the others), it calculates what action is required, adjusts the result for lateral acceleration (ie how fast the car is cornering) and then sends a signal to the appropriate solenoid. The solenoid moves an hydraulic valve, which cuts off the circuit from the driver’s brake pedal and prevents any increase in brake hydraulic pressure coming from the drivers foot. If this action is insufficient to restore traction, the control module sends a further signal which moves the valve even further, allowing the brake line drain fluid back to an accumulator, thus reducing the pressure to that brake. When the wheel stops slipping (ie attains the same speed as the other wheels), the valve is released, allowing normal pressure between foot pedal and brake. This control process is repeated at a rate of fifteen control cycles per second. The episode is completed by the operation of a pump which evacuates the accumulator chamber and returns fluid back to the master cylinder reservoir.

The ABS goes through a self diagnostic routine the first time the vehicle passes through 5 kph after turning on the ignition. You have probably heard the pumps operating during this BITE test. (Built In Test Equipment operation) The lateral accelerometer will give a voltage of about 1.2V at 1g right, 4.2V at about 1g left and about 2.6V when the car is running straight ahead. If the control module reads in excess of 0.6g either way for more than 120 seconds, an error is indicated. Either the lateral accelerometer is faulty, or the car is lying on its side.

As near as I could determine, the car had not fallen over, so a replacement lateral accelerometer was called for. A mere five hours of contortions and a few phone calls to fellow club members and I had the offending unit out from behind the instrument panel. I sourced a replacement part from Vette Connections in Melbourne. It only took thirty minutes to pull the instrument panel apart a second time and install the replacement unit.


Dashboard Restoration - Classic Carshome_dash

When enthusiasts consider restoration of dashboards there are two fundamental issues that must be considered:

  • The "finished appearance"
  • The quality of work - "Restoration" or "Repair"

Finish in any restoration is paramount to ensure the original aspect of the vehicle is maintained. As far as dashboards are concerned this comment relates directly to the texture and grain of the finishing material. Unfortunately, due to the passage of time, material in the original grain and texture is almost impossible to locate, however, professional restorers do have alternatives that are almost identical to the OEM finish.

Enthusiasts should ensure that this aspect is clearly settled prior to committing their unit to the restoration process. Professional restoration businesses will have material available that has been used in prior classic car restorations that has been found to be acceptable by the car clubs with whom they deal. They should happily provide references from these clients together with material samples for your consideration. Insist on the material you require! home_dash2

Dashboard restoration has been available for over twenty years but unfortunately, despite the advance in technology, only a small group of professional restorers have moved forward with these advances. The techniques of twenty years ago remain with us today and provide an extremely poor quality result that is actually a simple repair rather than a quality professional restoration. This method is known as "crack-fill and cover" which in essence involves the dash surface material cut away from the dash cracks, that are then filled with automotive body-filler putty. The area is then sanded and a vinyl sheet glued over the dash surface. Failure of this type of repair occurs very shortly due to the effects of heat and cold on the body-filler that causes movement under the dash skin. Lumps form and the material will eventually force itself through the dash surface material. This is a low cost, no quality, method that should be avoided at all cost!

Professional restoration companies have taken advantage of technology and, in cooperation with major chemical companies, have developed products ideal for restoration purposes. Original dashboards were filled with low-density foams, which over time actually die and turn to crumble. In a professional restoration this dead material is removed from the unit and replaced with sophisticated products that replace the original foam and provide lightweight strength and durability in the dashboard. This material is then handcrafted in shape and size of the original unit.

Enthusiasts are not always aware that dashboards actually shrink and warp through the passage of time and only professional restorers understand that this can only be remedied by a quality approach. This aspect is undertaken by the use of tooling jigs especially designed for the vehicle in question, which ensures a correct specification. Unfortunately, those in the industry who are not true professionals, ignore this issue and often dashes simply wont fit or look absolutely unsightly due to obvious gaps between body and dash.

An important part of any high quality restoration is the surface preparation of the unit prior to the vacuum forming of the finishing material. Specially prepared adhesives must be applied to a specially prepared surface if total bonding is to be successful. This involves professional treatment of both the material and the dash surface. Perfect bonding will only take place if heat relief provision is made on the dash surface. This is due to the extreme pressure and temperatures required in the vacuum forming oven process. Bonding will fail, due to air bubbles, in corners and instrument apertures if suitable relief is not provided.

The final finishing material must be of high quality to provide the UV protection and durability of the dashboard. Professional restoration businesses will only use OEM quality products. Colour should not be an issue to anyone, as professional restorers will use material that is pre-treated to accept quality colour dyes. Your dashboard should be available to you in any colour whatever. It costs no more to colour a unit black than it does to provide you red!

For further information see

By James A. Kirk


With the sky clear, the temperature moderate (before this heat wave), I think even the planets were aligned I decided to take the C5 out for a spin. Like most things, you never get enough time to do the things you want to do, so I was looking forward to a cruise.

Cover off, top down, open garage door, hope in, turn the key to start, flat battery “damn you Bundy”. Get the charger out, the battery boost cycle turns it a bit, but did no start the LS1. Garage door up, top up, cover on. Put it on charge for a while. 4 days later lets see the result. We have all heard that dreaded sound when she is trying to turn over but no cigar.

That’s it new battery . Well it ain’t a quick job. First the washer bottle has to be pulled out no real biggie.

Wash Bottle Comes Out and although C5s provide clear evidence that Corvettes have evolved a long ways since their inception, a man with tools hasn’t come too far from the apes.

But then you have to disconnect the battery easy, bloody long thin threads with no room to get you hand in. ½ an hour later the oddesy is out. Call my mate John Bondok he tells me if I do not want a oddesy get a optima. Call around, Battery World got em in stock off I go.

Fitting the battery, well it ain’t that easy, you have got to slide the battery one way first to fit the positive, then slide it back to fit the negative then after you have worked that out and it is connected you can’t fit the battery holder. So disconnect the negative put the battery holder on loose slide it around to refit the negative then tighten everything up.

Put back the washer bottle and stand back for ignition. Nothing sounds better then a car starting first time after you have done a battery let me tell you!

Oh by the way I purchased a battery charger that you can leave on all the time. Well it took 48 hours before it said this new battery was full. However I am pleased to say that I did not have the charger on for a week and the car started first go and the battery was full in 8 hours. I in my humble experience would say that these optima have won me over. In fact I put one in my 89 after that oddesy also had the Richard.

Time taken to pull out and fit about 2 hours, mucking around with bolts about 2 hours, Car starting 3 times after, when you want it Priceless. Keep the wave.

Tim McCarthy

I had originally thought of doing a technical column focusing on some of my projects such as supercharging a C5 or putting C4 suspension under a C1, or cold air induction. However, it seemed to me the question on everyone's mind was really do Corvettes float.fiberglass

The logic here is easy to see, boats are made of fibreglass, Corvettes are made of fibreglass so the question is “Can your weekend road warrior double up for a nice trip on the bay for a family fishing trip ?”

Corvette Owners being an adventurous lot, one owner decided to put this to the test with dubious results. It seems yes they do float but only for 8-10 minutes.

Some of the choicer comments from corvette forum members were :

The water box at that track is too deep!!!
We all live in a yellow submarine.
Is that a Stingray or a Shark ?
The names Bond, James Bond. Oh wait, that was a Lotus submarine car.
Stupid is as stupid does!
I guess he mis-understood the part about cars diving under braking!
This is the worst case of hydrolock I’ve ever seen !

Other comments were less complimentary. Seems the driver had a towbar on the C5 and was backing down a ramp with a trailer to collect a jetski. Witnesses said the corvette just kept reversing in until it was floating and the driver swam out.



1953The Corvette was introduced. Zora Arkus-Duntov joins Chevrolet


1954Work begins on a new OHV V8 engine


1955A Duntov prepared Corvette exceeds 150mph at Daytona Beach


The first major design change with the second generation Corvette. An optional hardtop was now available


1957Fuel injection now produced one horsepower per cubic inch on the 283 CID small block engine. Positraction rear axle is now available with 3.70:1, 4.11:1 or 4.56:1 ratios. Heavy-duty suspension was offered. Five optional 283 CID V8’s were offered with horsepower ranging from 245 to 283


The top Corvette engine was now 290 bhp. Was the first full year of Auto Manufactures “ban” on factory sponsored competition cars>


1959Metallic brake linings were offered


1960Was the first year for aluminium heads and radiators. Top bhp was now 315 via fuel injection


1961The aluminum radiator is made a standard item. A direct flow exhaust system is offered as a no cost option


A new 327 CID engine was introduced, with up to 360 bhp


A new third design generation Corvette arrived, with a unique “split” rear window on the Sting Ray coupe and roadster. Sintered metallic brakes were made optional. An off road exhaust system was offered. A performance package [RPO Z06] was offered for coupes only


1964A one-piece rear window replaces the split window on the coupe. Top engine option was 375 bhp. And a transistorized ignition was available


Four wheel disc brakes were made standard. RPO M22 four speed close ratio heavy-duty gearbox was made optional. A new telescopic adjustable steering column was offered


A top bhp 425 engine was via a Turbo-Jet 427 CID V8. Fuel injection was dropped


The width of the wheel rim was increased to 6 inches. Top bhp is 435


The fourth generation Corvette arrived [nick-named The Coke Bottle Shape]. The “Sting Ray” name was temporarily dropped. The width of the wheel rim was increased to 7 inches. Turbo Hydramatic transmission was made optional


A new 350 CID V8 was introduced. The “Stingray” [now a one-word emblem name] returned


A Turbo-Jet 454 CID engine was introduced. The top bhp was 390 from the LS5. 460 bhp is now available for competition on the LS7. A 350 CID small block V8 was introduced


The ZR1 factory racing option was available with 330 bhp CID engine. The ZR2 was available with 425 bhp 454 CID engine


Engine output was now SAE nett rather than SAE gross. The top engine option is the LS5 454 CID with 275 bhp. An anti theft alarm system was standard


An energy absorbing front bumper was introduced. The coupe’s removable rear window was now fixed. The LT1 engine was dropped. An L82 engine with 270 bhp was now available. The top engine is now the LS4 with 454 CID and 275 bhp


This is the last year for genuine dual exhausts and the 454 CID engines. The rear end was redesigned to accommodate government regulation 5-mph crash bumpers


Catalytic converters were added. This was the last year for the roadster. Solo engine option is now L82, rated at 205 bhp. A new high-energy ignition system was introduced


The L82 engine was now rated at 210 bhp. Aluminium alloy wheels were introduced later in the year


Leather seats were now made standard. Wiper, washer, headlamp dipper switches were moved to the steering column. Power steering and power brakes are now standard


Re-styling alteration to the rear window produces a fast back roofline. A limited production 'Silver Anniversary' and 'Indy Pace Car' [6,502] replicas were available. The wiper control was moved back to the dash! The L82 engine option was now 220 bhp


New 60 series radial tyres were offered. The L82 was now rated at 225 bhp. New lightweight bucket seats were introduced. [First used on the Indy Pace Car in 1978]


The “Areovette” was not introduced. The front/rear spoilers were integrated in the long running fourth generation body. A 305 CID California engine was made for that state only. The kerb weight was reduced by 250 lbs


A new glass-fiber reinforced plastic mono-leaf rear spring was adopted on all models with automatic transmission. Thinner side glass, stainless steel exhaust manifolds, lighter engine/interior materials were used to cut weight. The quarts clock and six way power seats are now standard.


A new drive train for the 1984 was introduced. The L83 engine features dual throttle body fuel injection [TBI] called “Cross-Fire Injection” by Chevrolet. Four speed overdrive automatic is the only gearbox available. The “Collector Edition” [6,759] features an opening rear “hatch”


Because of it’s late introduction in March 1983 and because the new Corvette met all 1984 government requirements, Chevrolet decided to skip the 1983 model designation. 1983 Corvette’s were built and serial numbered and the motoring press drove 1983’s at the “long lead” press preview for the Corvette at Riverside Raceway in December 1982. But 1983 Corvettes were not released for sale to the public and officially 1983 Corvettes do not exist.


Officially the fifth generation Corvette makes it’s debut to the public, 19 inches shorter, 500 to 600 lbs lighter, with a smoother more aerodynamic body-work, more glass and ally wheels with low profile tyres


Fuel injection returned to the Corvette after twenty years. Electronic digital dash was made more reliable


Corvette reintroduced the convertible [7,315] after eleven years. Major reinforcement of the convertible body resulted in the tightest new generation car to date


Similar structural improvements were made to the coupe this year. New suspension handling kit RPO Z52 gives the Corvette the best handling ever


This Corvette was similar to 1987. Wheels were bigger 17”x19½”. A thirty-fifth Special Edition was produced, with special paint, interiors etc


1989A six speed gearbox was specially built for this model. The 16” wheels introduced in 1988 were discontinued, twelve slot 17” were used and became standard


Corvette’s had improved brakes this year. Air bags were added. A new instrument panel was designed

Discerning members of the Queensland Corvette Club use and recommend fasteners from "bolts nuts screws on-line" for all of their home, mechanical, industrial and commercial fastening requirements.

Jimmy carries an extensive range of the best quality fasteners which can be ordered on-line and quickly couriered to your door.

Click on the nut or phone 1300 589 836 to place your order.

Grades of Bolts

An Engineer Rambles

Is it possible to write an essay about bolts? If you are a Engineer, and your livelihood depends on machine design, then its possible to write a book about bolts.

There are three grades of bolt in common use in Australia. Most bolts which you will come across will only deviate slightly from these three grades. The lowest grade is 4.6, commonly known as commercial grade. Next comes grade 8.8, known as structural grade, and finally, the highest grade is 12.9, known as high tensile bolts. The first number represents the ultimate tensile strength of the bolt, 400 MPa, 800 MPa or 1200 MPa respectively. The second number represents the point at which the bolt will permanently stretch. (Officially, the 0.2% proof load stress). A 4.6 bolt permanently stretches at 60% of its ultimate, an 8.8 at 80% and a 12.9 at 90 %.

Grade 12.9 bolts are most often supplied as socket head bolts or socket head cap screws with hexagon socket (Allen Key) drives. Corvettes use a lot of Torx drives, and there are other types of patented and tamper proof drives such as Safe-T drive. Grade 12.9 bolts can also be obtained with hexagon heads. Popular brands of grade 12.9 bolts are Unbrako and Holo-chrome. It is possible to obtain zinc or chrome plated versions, but not galvanised. Galvanising destroys the heat treatment of the steel. Beware! it is not possible to source 12.9 grade stainless steel bolts. 316 and 304 stainless steel will only be equivalent to grade 4.6. They may look cute in an engine bay, but they do not meet the grade. Grade 12.9 nuts are not made. Grade 8.8 bolts are usually supplied as hexagon head bolts, often galvanised, sometimes zinc plated, but usually black. They are distinguished by the three radial lines on the head, or these day, by the numerals 8.8 stamped on the head. Grade 8.8 nuts are taller than grade 4.6, but do not have any distinguishing marks

Grade 4.6 bolts come in a vast array of configurations. Hexagon head, countersunk slot drive, galvanised, zinc plated, oxy-sealed (ie gold zinc plating), chrome plated. On a motor vehicle, grade 4.6 bolts are used to hold on trim parts and light objects. Grade If you need to replace a bolt, and the grade is doubtful, use grade 8.8 and be safe. The head of a grade 4.6 bolts is easily scratched with a file, not so a 8.8 bolt.

Correct design of a bolted joint is quite involved. Serious joints are designed on the basis of maximum stretch in the bolt, with minimum cyclical fluctuation of stresses in the bolt under working conditions. In order to achieve this aim, high tensile bolts are pre-tensioned, bolts are made as long as possible, and the minimum size bolt is used. Often the shank of a bolt (ie a cylinder head stud) is reduced in area to assist. Bolted joint design too complex to delve into here. The average Corvette enthusiast will be replacing bolts in an existing designed joint and need not worry to much about the design of joints.

How do you tighten a bolt?

Grade 12.9 bolts are tightened with a torque wrench, right up to their 90% proof load. There is no other effective way to tighten a grade 12.9 bolt. Automotive manuals will give the tightening torque required. Grade 12.9 bolts do not work effectively with spring washers or shakeproof washers. These don't bite into the hardened surface of the bolt. There are only two ways of adding extra security to grade 12.9 bolts. Use Loctite on the threads or drill the heads and wire the bolts. It is possible to buy pre-drilled cap screws. Mating surfaces of a 12.9 bolted joint are not painted. For serious work, never re-use a fully tensioned 12.9 bolt.

Grade 8.8 bolts are tightened by the part turn method, torque wrench, or by using load indicating washers. In the part turn method, the bolt is done up to snug tight, and then advanced one, two or three flats of the hexagon, depending on the size, length etc. The torque wrench method is used commonly, often in the form of an air operated rattle gun. Special load indicating washers, such as Coronet washers can be used. These have dimples which indent the mating surface. A feeler gauge is used to determine the pre-load. Grade 8.8 Bolts are used in High Strength Friction Grip applications. If this is the case, the mating surfaces must not be painted or galvanised. For added security of the joint , use any one of the plethora of systems such as spring washers, shakeproof washers, Loctite, wired heads, split pins and castle nuts, locking tabs, lock nut or patented nut systems (Nyloc is common). For serious work, use castle nuts, either with split pins or wired together in groups. Also for serious work, do not re-use fully tensioned grade 8.8 bolts, Nylocs, split pins etc.

Grade 4.6 bolts are not pre-tensioned in the joint. They are tightened to snug tight only. For all intents, this means a reasonable hand effort on a spanner. Use good springy chrome-moly spanners, and never put an extension bar on the spanner. All of the security systems available for 8.8 bolts are available on 4.6 bolts. If you need much more than a spring washer, question whether the joint really requires an 8.8 bolt. Mating surfaces of a grade 4.6 bolted joint are usually painted prior to assembly.

Brake Fluid
Owning and running a classic Corvette can be a rewarding experience, we all love our cars,
maintaining and replacing fluids, our engines blood, is an essential part of any vehicle’s
maintenance schedule.
Sometimes one of those systems that does not get as much attention as needed is our brake fluid.
Most brake fluids used today are glycol-ether based. Glycol-ether (DOT 3, 4 and 5) brake fluids are
hygroscopic, which means they absorb moisture from the atmosphere.

Glycol-based brake fluid starts to absorb moisture from the moment it is put in the hydraulic brake
system or exposed to the air. The fluid attracts moisture through microscopic pores in rubber hoses, past seals and exposure to
the air.

An easy way to test your fluid is to get an electronic brake fluid tester available from most
automotive stores.
Looks like this

Brake Test

It will tell you the condition and moisture content of your brake fluid. Depending on the results you
may wish to have a brake flush performed on your system.