Anyone who’s driven a car with a manual transmission long enough knows the feeling: The engine is revving and making all the cool sounds that it normally does, but something’s not quite right.
“Hey, it sounds like it’s revving a little faster than normal,” you foolishly tell yourself, a cool sense of satisfaction creeping outward. “It must be running really good right now.”
Then reality hits, immediately spiking the mood downward: “Wait, why isn’t the car moving forward at a speed proportional to the increase in revs? Also, what’s that smell? I don’t recall burning anything in the toaster recently.”
Ah yes, the sights, sounds and smells of the roasted clutch. We received this lovely sensory experience at a local autocross. Instead of milking out another run or two, however, we decided to put the car on the trailer before damaging things further.
Overall, though, we couldn’t complain. This was the original clutch, one that had survived nearly 100,000 miles in our 2004 Corvette Z06. It had lived a good life. But now it was time for a well-earned upgrade.
For a replacement we went with a single-disc, 10.4-inch-diameter unit from Quarter Master. The brand’s Optimum SR clutch is a nice “one box” solution that includes a clutch, flywheel, release bearing and the proper alignment tool.
Then we had to install it. One note about this job: It’s complex, but not completely out of reach for the home gamer. We called in the experts for this one, however, so we could pass along their knowledge.
Now that we’ve watched The Vette Doctor’s factory-trained techs complete this project in their Central Florida shop, we’d probably be comfortable tackling the job on our own if we ever had to do it again. (We hope we don’t have to, though.) Looking back, we’re glad we didn’t attempt it on our own the first time. There are more than a few “traps” awaiting those unfamiliar with the process.
1. Start by getting some big stuff out of the way. This includes the exhaust and rear subframe, which comes out with the lower control arms attached.
2. You need some distance between the car and the ground–no way around that. Even with tall jack stands you’d be cutting it pretty close, so if you have access to a lift, exploit it. You also need a secure way to lower the transmission and torque tube. Trap number one: Do not use a floor jack, as the assembly needs to be held steady as it descends. A dedicated transmission jack is the right tool for the job.
3. The tunnel cover comes off next. Hope you brought power tools, because it’s secured with about 300 bolts. Once they’re removed, the cover can separate from the rear of the engine, exposing the bottom of the flywheel.
4. Now you can slightly lower the transmission and rear end, keeping them connected to the torque tube, to access all of the bolts securing the torque tube to the engine. Here’s where you’ll encounter the most perilous trap: do not lower the transmission so much that the back of the engine hits the firewall. Bad, bad things will happen if it does. There’s actually a warning sticker about this affixed to the torque tube. (You did look for warning stickers before you started, right?)
5. Once clear of the car, your transaxle, diff assembly and torque tube should look like this (minus the dope C3s in the background). If they don’t, go back and make sure you haven’t destroyed your car. The old clutch and flywheel should now be accessible and can be removed.
6. Our old clutch and flywheel actually didn’t look horrible considering how much they’d been slipping-some glazing and hot spots, but less than we expected. Still, this clutch had clearly lived a full life and was ready to go to a better place.
7. Now that the rear engine cover and rear main seal are accessible, let’s discuss the “while we’re in there anyway” phase of Corvette clutch work. You’d be crazy to skip WWITA jobs at this point, since you could end up redoing all of this labor in the near future just to replace a relatively inexpensive part. Still, lots of inexpensive parts add up, so in addition to $3000 for the Quarter Master clutch and flywheel, spot yourself several hundred bucks more for WWITA bits like a rear cover, drive couplers, and torque tube bearings and seals.
8. Speaking of our Quarter Master parts, here they are. Not only are they capable of handling 700-plus horsepower and 500-plus lb.-ft. of torque, they’re 25 percent lighter: about 35 pounds versus 50-plus-pounds for the stock assembly. That’s a nice reduction in rotating mass.
9. Time to tackle some more WWITA work. First, disassemble the torque tube to install fresh seals, bearings and drive couplers. The current pieces may look fine, but if you have a high-mileage car, replace them anyway in the spirit of preventive maintenance. To remove the horseshoe crab-sized C-clip from the front of the torque tube, you need a huge-ass set of C-clip pliers. Buy, borrow or rent some if necessary. Avoid the trap of attempting this step with the wrong tool: Should you manage to keep all of your digits intact, you’ll be lucky to ever see that C-clip again. It will surely find the deepest, darkest corner of your shop.
10. This is why you replace the drive couplers. They’re rubber, they get old and fatigued, and they crack. We replaced ours with OEM pieces since they can handle a moderate power bump and still provide factory levels of driveline cushioning. Upgrades are available in urethane and solid metal, but remember that any increase in stiffness comes with a proportional increase in driveline harshness.
11. The sensors and vents on top of the transmission can leak. Ours showed more or less the correct level of fluid seepage and dirt accumulation, so we left them alone. If yours look worse or have active drips or wet areas, this is a great time to replace some seals and gaskets.
12. Another WWITA work opportunity: Since the axle shafts have to be removed from the differential, you can now easily access the rear hubs. We upgraded to ARP wheel studs and some fresh SKF bearings.
13. Assembly is, as they say, the reverse of removal. We’re not going to lie to you, it’s a big job. The professional techs working on our car put more than 10 hours into removing the assemblies, rebuilding the torque tube, and reinstalling everything–and they do this job on the regular. Budget your time accordingly if you’re going in yourself. We also highly recommend a proper alignment once the car is back together, since a good chunk of the suspension gets removed and reinstalled.
14. The stroke of the Quarter Master clutch is much shorter than stock, and overstroking it can lead to premature spring wear down the road. So we built a simple clutch stop from a piece of quarter-inch threaded rod, with a wire nut on the end to provide some cushioning. We bypassed the clutch safety switch with a jumper wire. Usually “bypass” and “safety” are not words you want to read in the same sentence, so please don’t blame us if you start your car and it drives away from you.
15. While the car is down for service, it’s a great time to get an underhood mural done. Here’s some inspiration.
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