Beginning in 1997, the C5 Corvette’s 6-speed manual and automatic gearboxes were attached to the rear differential at the back of the car. Unlike traditional rearwheel- drive cars that have the driveshaft behind the engine and transmission, the C5’s is located between the engine and transmission. The main benefit of this configuration is so that engineers could design a near-perfect 51/49-weight distribution into the new car. Both fifth and sixth gears in the 6-speed are overdrives: 0.74:1 (fifth gear) and 0.50:1 (sixth gear), respectively.
This Tech Tip is From the Full Book “HIGH-PERFORMANCE C5 CORVETTE BUILDER’S GUIDE“. For a comprehensive guide on this entire subject you can visit this link:
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This radical driveline design was a departure from all previous Corvette models. The new C5’s transmission was located in front of the rear differential. The clutch and pressure plate remained mounted to the engine. A torque tube enclosed the driveshaft, which connected the flywheel, clutch, and pressure plate to the transmission. The driveshaft rotated on two large, fiber composite bushings attached to the front and rear of the torque tube. The shifter linkage runs along the tube to the transmission. While this was a radical design departure for Corvette, the rear transmission concept has been used on other exotic sports cars, like Ferrari, for years. Another reason Corvette engineering shifted to this approach was to provide more interior room in the new car. With a front engine design, engineers always try balancing the car’s weight to the ideal 50/50 distribution. Moving the transmission to the rear also enabled them to move the engine behind the front axle. The rear-mounted transmission and axle housing are bolted to a large aluminum cradle. This cradle is secured to the frame by four bolts. The rear suspension, spindles, lower control arms, brakes, sway bar, and springs are also mounted to this cradle. The engine is mounted to a large aluminum cradle at the front of the car. In addition, it has the suspension spindles, lower control arms, front sway bar, brakes, and anti-lock braking- system module attached. This cradle is held in place by four bolts that attach it to the frame. Lift the car into the air and, once the cradles are supported, then remove the eight bolts and the entire driveline from the car. Most shops prefer this method if they have to perform any major mechanical repairs to a C5.
The C5 has two rear axles connected to the rear uprights via a wheel bearing. The axles are splined on the inside and fit into the rear-end housing; they are held in place by clips. Both ends of the axles feature universal joints covered by rubber boots that protect them from weather-related damage. All of the engine’s torque and horsepower are transmitted through these axles to the rear wheels. Sticky tires like drag radials really take their toll on these units. I strongly recommend changing these to stronger aftermarket units if you plan to continuously drag-race your ’Vette.
The C5 driveshaft is encased inside an aluminum torque tube. The torque tube is attached to the engine bellhousing in the front and to the transmission case in the rear. The driveshaft is held in place by bearings inside the torque tube. In 2001, a stronger driveshaft was put into all C5s to cope with the higher performance of the Z06. The driveshaft was changed from a metal matrix composite to aluminum alloy 6061, and was increased in diameter from 55 mm to 63 mm. Driveshaft couplings also were upgraded on manual-equipped models for additional strength and durability.
Rear End The C5 rear end is mounted on the rear chassis cradle, and the automatic or manual transmissions are bolted to the front of the rear-end case. C5 Corvette automatics were equipped with a standard 2.73:1 axle ratio and an optional 3.15:1 ratio. All 6-speed cars came standard with a 3.42:1 ratio.Servicing
The rear-end axle side covers have a tendency to leak differential fluid, especially the one on the driver’s side. If you are buying a C5, it is important to review the car’s service history to see if this problem occurred and was fixed. I strongly recommend routinely checking this part of your differential, because loss of fluid could have expensive consequences. Each time you have your car’s oil changed, make sure the technician checks the level and condition of your differential fluid.
Removing and Replacing
This job requires a proper lifting device, tools, and a Corvette service manual for your year vehicle. Follow the service manual step by step if you have never done this before. Removing, servicing, and replacing the rear axle assembly in a C5 require removing major mechanical components in the car. This job is much easier with two people. So here we go: start by removing the wheels, the exhaust system, and the rear brake calipers. You can leave the brakes attached to the suspension upright or remove the calipers from the rotors. If you take the calipers off the rotors, support them with a bent piece of wire connected to the frame.
Next, the upper control arm bolts on the rear suspension need to be removed from the frame (See top photo page 70). The shocks also need to be unbolted on the bottom of the lower control arm. The rear suspension cradle and the rear of the torque tube need to be supported with adjustable safety stands. The four rear cradle bolts and all associated wiring need to be released. The rear of the torque tube needs to be unbolted from the transmission. Once everything is properly released, the rear cradle needs to be lowered via the safety stands. Once the cradle clears the four bolts, the entire unit is slid back away from the torque tube. Next, the transmission needs to be removed from the rear end
The rear end can now be serviced on the cradle or completely removed and serviced on a workbench. Just reverse the removal procedure to reinstall either unit. Again, this job is much easier if you have access to a vertical lift. It can be done on the ground with safety stands, but the preferred method is using a lift.
Three transmissions were offered for C5s from 1997 to 2004: the M-30 automatic (option code MNO), the MNO (6-speed), and the M-12 (Z06 only). The automatic is a 4-speed overdrive unit that came standard with the GU2 rear axle (2.73:1). This transmission was also available with the G92 performance axle (3.15:1). All 6-speed cars were equipped with the GU6 axle (3.42:1), including the Z06.
M-30 Automatic Transmission (4L60-E)
This transmission was introduced to the C5 in 1997. It continued to be the only automatic transmission available in the C5 to the end of production in 2004. It came standard with a 2.73:1 final drive ratio, and the 3.15:1 performance axle was optional. In later C5s, a lighter automatic transmission case was installed. By optimizing the design of the automatic transmission case, Corvette engineers were able to trim some material and reduce thickness in some areas. This resulted in a weight reduction of 3.3 lbs without sacrificing reliability. This transmission is modified by a number of aftermarket tuners for drag racing.
M-12 6-speed Manual
This transmission is unique to the Z06 and was introduced in 2001. It is the only transmission available for the Z06. It has more aggressive gearing (see the above chart) to increase torque multiplication in most forward gears, allowing for more rapid acceleration and more usable torque at higher speeds. A transmission temperature sensor was added to protect the M-12 from higher thermal stresses. The sensor warns the driver via the Driver Information Center with a “TRANS OVER TEMP” light if thermal loads become excessive, meaning that the transmission could be damaged if not allowed to cool down.
Carbon blocker rings have been installed on all manual-transmission forward gears to provide for smoother shifts and additional robustness.
The transmission fluid levels should be checked at every oil change. Oil changes are also a good time to inspect your transmission for any leaks that could damage your car or transmission. Consult your owner’s manual to determine the manufacturer’s recommended fluid changing schedule.
Removing and Replacing a Six-Speed or Automatic Transmission
This job requires a proper lifting device, tools, and a Corvette service manual for your year vehicle. Follow the service manual step by step if you have never done this before. Removing, servicing, and replacing the 6-speed or automatic transmission in a C5 require removing major mechanical components in the car. This job is much easier with two people. Start by removing the wheels and the exhaust system. Next, the upper control arm bolts on the rear suspension need to be removed from the frame. The shocks also need to be unbolted on the bottom.
The rear suspension cradle and the rear of the torque tube need supporting with adjustable safety stands. The four rear-cradle bolts and all associated wiring must be released. The rear of the torque tube needs to be unbolted from the transmission. Once everything is properly released, the rear cradle needs to be lowered via the safety stands. Once the cradle clears the four bolts, the entire unit is slid back away from the torque tube. Once this part of the driveline is clear, it can be lowered and moved out for servicing. Just reverse the removal procedure to reinstall either unit. Again, this job is much easier if you have access to a vertical lift. It can be done on the ground with safety stands, but the preferred method is using a lift. Clutch and Pressure Plate
All Corvettes with the 6-speed manual transmission (optional on coupes and convertibles, standard on Z06), feature a revised clutch with greater clamping power to accommodate increased engine torque. This new clutch design also provides for lower pedal effort, making manual-equipped Corvettes easier to drive. The pressure plate and clutch mechanism are operated with the clutch pedal that is assisted by a hydraulic piston to lighten the pedal pressure. The pressure plate is multi fingered and the pressure plate, flywheel, and clutch weigh about 60 lbs.
Lightweight flywheels, pressure plates, and clutches are available from the aftermarket. These units usually weigh 24 to 28 lbs. Because this unit is bolted directly onto the engine crankshaft, reducing this weight really improves engine performance. However, the lighter clutches and flywheels make it more difficult to drive a 6-speed car. Less flywheel mass means the car stalls more easily unless you keep the RPM at higher levels under starting conditions. Servicing
The clutch really does not require any routine servicing, except making sure the clutch master cylinder is filled to its correct level. Many people think brake fluid is used in Corvette hydraulic clutch systems. In the late 1980s, as a solution to squeaky clutch master cylinders, GM developed a specific clutch fluid (PN 12345347) and it is specified for the C5.
Removing and Replacing
This job requires a proper lifting device, tools, and a Corvette service manual for your year vehicle. What I am providing in this explanation is just an overview on what is required to complete this job. Follow the service manual step by step if you have never done this before. Removing and replacing the clutch in a C5 requires removing major mechanical components in the car. This job is much easier with two people. Start by removing the wheels, rear brake calipers (if you do not want to bleed the brakes), and the exhaust system. Next, the upper control arm bolts on the rear suspension need to be removed from the frame. The shocks also need to be unbolted on the top. The rear suspension cradle and the front of the torque tube need supporting with adjustable safety stands. The rear of the engine must also be supported with a safety stand to keep the engine in place when the torque tube is removed. The four rear-cradle bolts and all associated wiring need to be released. The front of the torque tube needs to be unbolted from the bellhousing. Once everything is properly released, the rear cradle needs to be lowered via the safety stands. When the cradle clears the four bolts, the entire unit is slid back away from the engine. Once this part of the driveline is clear, it is lowered and moved out of the way. Next, remove the lower bellhousing dust cover. This gives you access to the clutch assembly. The pressure plate and clutch can now be removed from the flywheel by unbolting the pressure plate. Once the pressure plate and clutch are removed, you can now inspect the flywheel. If it is warped or scarred from abuse, replace it. If it is in good condition, clean the surface and reuse it. If you want to use an aftermarket flywheel, this is the time to install one of these units.
Selecting Correct Clutch for Your Requirements
If you are just replacing the factory clutch and pressure plate, you are ready for reassembly. Just reverse the removal procedure and torque all of the bolts per the factory shop manual. Count on at least eight hours for this job. If you are going to install a lightweight aftermarket unit, first you must remove the factory flywheel. Because this is a pretty involved job, I strongly suggest you do some research on the type of clutch you are going to require. Because of their high, unsprung weight, the factory Z06 clutch unit offers you good reliability with high performance. If you are only slightly modifying your engine, and you are going to use your car for everyday driving, I recommend installing one of these units. Their mass allows smooth starts and they very rarely chatter. This makes driving in bumper-tobumper traffic much easier. However, if you are going to perform major engine work, like upgrading the head, cam, and block, you need to upgrade your clutch. As I have suggested before, talk with Corvette owners who have made this change or visit some Internet Corvette chat rooms before purchasing one of these clutch assemblies. Once you have your new clutch in hand, just reverse the removal procedure.
Engine cooling is critical to the longevity of your LS1 or LS6 engine. A few common-sense maintenance checks are sure to keep you car running in tip-top condition. Coolant put into LS1s at Bowling Green is a mix of 45% tap water and 55% ACDelco, Dex-Cool, a unique ethylene- glycol antifreeze with a non-silicate, anticorrosive chemical package. Dex-Cool was jointly developed by GM and Texaco and became factoryfill in most GM cars for the 1996 model year and newer. It is available at dealerships and auto parts stores under a variety of brand names. Just be sure to look for the GM-approved logo on the label. Its non-silicate formula is longer lasting and better for durability of cooling system parts than silicate-based anticorrosive packages in old-style antifreezes. Dex-Cool has an orange-pink color and has proven to be very reliable in Corvettes. If small additions of coolant are necessary, distilled water will suffice. If a large addition of coolant is required, first find the leak. Then add a 50/50 mix of distilled water and Dex-Cool. We suggest distilled water because tap water in some areas may be more acidic or have more alkaline than in Bowling Green.
C5’s coolant change interval is five years or 150,000 miles, whichever comes first. As good as Dex-Cool is, that interval seems long. Thus, I suggest changing coolant in LS engines at three years/90,000 miles. If you are changing coolant, mix Dex-Cool and distilled water at approximately a 50/50 proportion. Avoid antifreeze products other than Dex-Cool, unless antifreeze with a silicate anticorrosive package is unavoidable. However, as soon as Dex-Cool is available, drain the coolant, flush the system with water, and refill with the Dex-Cool/water mix. A good cooling system performance upgrade is the addition of Red Line Oil’s SuperCool. It consists of a chemical surfactant or “wetting agent” that improves heat transfer from engine parts to the coolant, along with a non-silicate, anticorrosive package. Adding SuperCool in the manufacturer-recommended proportion results in the coolant stabilizing at a lower temperature, once the thermostat is open. Other additives are unnecessary and do not use the “sealing pellets” that were recommended in past model years. They restrict parts of the cooling system and, due to improved technology in engine parts that come in contact with coolant, are unnecessary.
Cooling system work may involve hot liquid. If the engine is at operating temperature, it’s possible that coolant surge tank cap removal will cause an explosive boiling in the system. This could result in potential injury. The C5 tank cap is threaded to allow simple pressure relief. If the cooling system is hot, turn the cap 1/4 of a turn. When the hissing stops, turn the cap further until it comes off. If the engine is running hot, say, with a coolant temperature of 220 F and above, allow the engine to cool before removing the cap.Changing coolant in an LS1 is a little more time consuming than it was with older Corvette engines, because the engine block coolant drains are not accessible when the engine is in the car. The left drain is hidden behind the engine mount bracket, and the right drain is behind the starter. Because of this, you can’t fully drain the system; you only can flush it. This work may also involve working with hot engine parts or hot liquid. We suggest you use some automotive work gloves such as those sold by Mechanix Wear. We like them because they protect hands but still allow good feel.
The radiator drain is at the lower-right corner of the radiator. Open it and let it run until the flow stops, close the drain, and refill the system with water. Run the engine until the thermostat opens, shut off the engine, carefully release the pressure in the cooling system, and open the radiator drain again. Repeat this procedure until the coolant coming out of the radiator runs clear. You may need to do this tedious flushing trick several times to get the water to run clear. Once the flushing is done, close the drain and fill the system with 6.5 quarts of Dex-Cool (50%) and, optionally, a bottle of SuperCool additive (Check with your dealer before you do this). Add distilled water until it reaches the base of the surge tank neck. Start the engine and let it idle for a minute, then cycle engine speed from idle to 3,000 rpm and back, until coolant temperature reaches normal operating temperature. Remove the tank cap, observing the cautions discussed previously. The coolant level should be about 1/2 inch above the “cold full” mark on the tank. If it is not, top off with distilled water, replace the cap, start the engine, and repeat the above procedure.
Most C5 fuses, circuit breakers, and relays are away from engine heat in a compartment behind the right front wheel next to the battery. The PCM is in yet another cavity under the battery, which is a problem with C5s. Because of engine heat, batteries sometimes leak and the battery acid damages the PCM, which sits right under the battery. When buying a C5, be sure to carefully inspect this problemprone area. Removing the right wheel-well filler-panel exposes it. Additional fuses and circuit breakers, mainly interior and instrument panel cluster (IPC) items, are located under an easily removable panel at the front of the passengerside foot well under the carpet.
The alternator on a C5 is the dependable ACDelco CS130D series unit. CS130Ds are quite durable, but should you ever have to replace one, the job is easy. The alternator is driven by the customary serpentine belt system, but the LS1 uses two belts—one for the HVAC (Heating, Ventilation, Air-Conditioning System) compressor and the other for the alternator and accessories. The air filter element is contained in an easy-to-open housing in front of the radiator. The factory element is an ACDelco A917C. It should be inspected every 10,000 miles and replaced, if necessary. A common performance upgrade is the oilimpregnated, gauze filter (PN 33- 2111) from K&N Engineering. While the initial expense of the K&N may be higher, eventually it becomes a better value because all K&Ns are reusable. Inspect it every 10,000 miles. If it is at all dirty, simply remove it, clean it, re-oil it, and put it back in place. The alternator on a C5 is the dependable ACDelco CS130D series unit. CS130Ds are quite durable, but should you ever have to replace one, the job is easy. The alternator is driven by the customary serpentine belt system, but the LS1 uses two belts—one for the HVAC (Heating, Ventilation, Air-Conditioning System) compressor and the other for the alternator and accessories. The air filter element is contained in an easy-to-open housing in front of the radiator. The factory element is an ACDelco A917C. It should be inspected every 10,000 miles and replaced, if necessary. A common performance upgrade is the oilimpregnated, gauze filter (PN 33- 2111) from K&N Engineering. While the initial expense of the K&N may be higher, eventually it becomes a better value because all K&Ns are reusable. Inspect it every 10,000 miles. If it is at all dirty, simply remove it, clean it, re-oil it, and put it back in place.
Written by Walt Thurn and Posted with Permission of CarTechBooks