The clutch is one of the major wearing parts in manual transmission equipped Corvettes. In part 1 of this series we showed the tranny removal. Now let’s take a look at parts options, important inspections and assembly details. Also sprinkled in are some time-saving tips not found in the factory service manuals.
Clutch part costs are very reasonable for stock replacements. Car enthusiasts generally think bigger and stronger are always better. However, when it comes to a clutch assembly for a street driven car with less than 400 horsepower, more is not necessarily better. A bigger, stronger clutch may increase pedal effort dramatically, which can make the driving experience unpleasant.
The Paragon clutch plate assembly we installed does not punish your wallet or your left leg. It includes a new clutch disc, pressure plate, throwout bearing, pilot shaft bushing and alignment tool … all for well under $200.
As with most labor-intensive repairs, it’s wise to think about other things to replace while you’re there. Foremost is any needed transmission work such as replacing the rear seal. Equally labor-intensive is replacing the clutch fork, shifter assembly, underbody tunnel insulator and foam collar, or flywheel and ring gear.
Several other parts have a lesser degree of labor overlap but it will still save some future effort if they are replaced at the same time as the clutch. You may discover the need to replace driveshaft U-joints, the clutch boot or linkage, exhaust manifold gaskets, exhaust pipe clamps, the bellhousing front cover or the transmission mount. It’s also a good time to clean, lubricate and adjust the shifter. Paragon offers many of these parts, including bellhousing bolt kits and other fasteners should they be needed.
After the clutch is removed, inspecting the parts before reassembly is an important task that should not be rushed. Attention to detail will make sure the clutch installation has a happy conclusion.
01. The wear surface of the flywheel shouldn’t have heat cracks or deep gouges but it does not have to be perfect. This flywheel is fine even though it has over 300,000 miles of use, with much of it city driving. Also note the drilling and white marks. This is evidence that the engine was balanced at some time with the flywheel installed. That’s a good reason not to replace it.
02. Carefully inspect all the teeth on the ring gear. Install one pressure plate bolt to keep track as you turn the crank using a breaker bar or torque wrench and an 11/16-inch socket on a flywheel bolt. If any of the teeth are damaged, now is definitely the time to change the flywheel.
03. Also inspect the pilot shaft bushing. This bushing doesn’t wear much because it only moves relative to the transmission input shaft when the clutch is held in. The original bushing was bronze and is inexpensive but be forewarned that it is often no longer stocked by the major auto parts stores. Paragon includes a roller bearing with their clutch assembly.
04. The flywheel is attached to the crankshaft by six bolts with star washers. I prefer to apply thread locker before torquing them. The flywheel can be prevented from rotating while torquing these bolts by installing a pressure plate bolt from the opposite side so that it contacts the block.
05. Use a brake cleaner, acetone or a similar clean-drying solvent to make sure that the contact surfaces of the flywheel, pressure plate and clutch disc are completely clean and free of greasy fingerprints or protective oil coatings, such as Cosmoline. A slight amount of grease or oil here can cause a nasty chattering of the clutch.
06. After wiping with solvent, I like to sand the pressure plate and flywheel to make absolutely certain no traces of oil or grease are left on the surfaces that mate with the clutch disc.
07. Make sure the clutch disc slides freely on the splines of the transmission input shaft. It’s much easier to test that all the new parts fit OK before assembly than to discover a problem later.
08. Insert the alignment tool through the clutch disc and into the pilot shaft bushing. Make sure the damper springs of the clutch disc face rearward and do not contact the flywheel bolts.
09. Install the pressure plate. After the bolts are just snug, forcefully wiggle the alignment tool up and down and side to side to help center the clutch disc. Then tighten the bolts about a turn at a time until the pressure plate housing contacts the flywheel.
10. Note that the pressure place is attached with six shoulder bolts and lock washers. Replacement bolts should not be threaded all the way to their head. The torque on the pressure plate would crush threads and allow movement with respect to the flywheel. The six bellhousing bolts have a shoulder and a flange. Paragon offers replacement sets.
11. Inspect the clutch fork and boot. Either set of spring clips on the fork can be bent or broken due to improper installation. The rubber boot is often brittle or torn. Both parts are available from Paragon.
12. Lubricate the ball socket of the clutch fork before installing it. Look inside the bellhousing to make sure both clutch fork clips are contacting the flat rear side of the ball stud. Sometimes it takes effort to make the spring clips engage the ball stud properly. The fork should move freely and easily.
13. Clean the mating surfaces and then install the bellhousing. Install the throwout bearing with its bearing (big) side forward. People often make the mistake of not getting both of the fork’s spring clips inside the groove in the bearing assembly as shown.
14. Don’t forget any bracket or ground wire attached by the bellhousing bolts. If this black wire is not grounded, the heater fan and windshield wipers may not work.
15. Before tightening the bellhousing bolts, check that the front cover’s tabs are properly engaged with the lip of the oil pan. If not, there will be quite a racket when the engine is started.
16. Lock up the transmission by turning either front shaft to shift it into any forward gear and then turning the rear shaft to shift into Reverse. This helps when inserting the transmission into the clutch assembly. By rotating the transmission a little, the splines of the input shaft are forced to turn and engage into the splines of the clutch disc.
17. Insert the transmission into the bellhousing and slide it forward until the transmission contacts the bellhousing. It should go nearly all the way in. If anything more than minimal force is needed on the transmission bolts to draw the transmission into the bellhousing, stop and find out what’s wrong.
18. Remove the shift levers one at a time from the shifter assembly. Clean and inspect them before applying a little grease and reinstalling them. Install the shifter bracket, the transmission mount bracket and the shifter assembly. The shifter’s two mounting bolts are the most tedious part of the entire job. Tip: snug the lower bolt first.
19. Twist the U-joints on the driveshaft to make sure they move smoothly and freely. Install the exhaust mounting bracket and transmission mount. Lower the engine and reconnect the shift levers, speedometer cable, brackets and wires to the transmission. Install the header pipe and tighten the clamps. The bulk of the job is complete.
20. If you’re wondering about the little tabs on the clutch fork rod, they are for attaching springs that keep each end from rattling. It’s not uncommon for these springs to be missing.
21. Use a 5/8-inch open end wrench to tighten the ball stud that screws into the engine block. Engine vibration often loosens this. Use the zerk fitting in the bellcrank to grease both ends.
22. Use a 9/16-inch wrench to check that the nut that holding the clutch bellcrank to the frame is tight. The factory installed a special clip to keep it from loosening but the clip is frequently missing or damaged.
23. Remove the clutch pedal rod from the upper side of the bellcrank. Clean, inspect and reconnect it before adjusting clutch free play via the two nuts. If you feel spry, try lubricating this rod at the clutch pedal end.
24. Check to make sure there is at least 1 inch of free play at the clutch pedal. As the clutch wears, this free play will decrease and require further adjustments. If there is no play at the pedal, the throwout bearing, clutch disc and pressure plate will wear out rapidly and prematurely.
25. Engines that are far stronger than stock can benefit from high-performance clutches like the Street Slayer from American Powertrain. It has Ceramix pads and is rated at 545-755 lb-ft of torque.