Clutch technology has always been about getting a grip and getting power from the crankshaft to the rear axle. How to do that successfully has always been the challenge for clutch manufacturers like McLeod, which has been designing and manufacturing clutch systems since it was founded nearly a half-century ago.
When you’ve been making clutches for as long as McLeod you come to learn a thing or two about how to develop and engineer them for a wide variety of street and racing applications. The objective is to get a clutch to hook up without slippage and do it consistently for years and years and thousands of miles. As we continue to add to the horsepower and torque burden it becomes tricky to produce a clutch that can stand up to the power we want. This is why we looked to McLeod and their Super Street Pro clutch for our LS application.
The McLeod Super Street Pro clutch (PN 75223) for LS applications can take up to 550 horsepower along with comparable torque, which makes it ideal for both the street and track. This SFI-approved clutch and flywheel combo includes a high clamp load pressure plate and a dual-faced organic and metallic clutch disc for smooth engagement and terrific holding power. Organic provides smoothness while metallic gets the grip.
When it comes to clutch friction material, there are several types of frictions for specific missions. There’s organic and heavy-duty organic for medium-duty street use. Ceramic clutch friction material consists of copper, iron, tin bronze, and silicon dioxide mostly. Because the ceramic clutch facing tends to engage abruptly, it isn’t suggested for street use. However, it is perfect for racing. Kevlar is a nice compromise for street and strip applications because it is so rugged yet forgiving because it offers both durability and smooth engagement. Metallic clutches offer durability and smooth engagement. They are designed primarily for truck use.
What’s nice about these McLeod clutch kits is they arrive with everything you need to perform the installation, including the pilot tool, release bearing (where applicable), and pressure plate bolts (where applicable).
We also opted for the McLeod hydraulic clutch slave/release bearing package (PN 1372) to replace the aging factory unit. It is a drop-in replacement, which doesn’t involve any special modifications. All you need to do is bleed the system upon installation and do an operational check before hitting the road and you’re good to go. CHP
1. After making room by removing the driveshaft and the exhaust system, the hydraulic clutch braided line needs to be disconnected at the master cylinder above. Have a drip pan available for the stray brake fluid in the system and be careful not to get it on any painted surface; it will do permanent damage.
2. The shifter handle is disconnected from the shifter by removing two bolts with a 5/8-inch box-end wrench.
3. Because we’re working with the TREMEC T-56 Magnum six-speed transmission, it is virtually impossible to remove the transmission and bellhousing together because the bell will not clear the transmission tunnel. If this was a TREMEC TKO five-speed, there would be enough room to clear the tunnel.
4. Technician Gary Nelson supports the T-56 Magnum with a transmission jack, working the transmission loose from the bell.
5. With the transmission properly supported, Gary removes the crossmember for easy transmission removal.
6. We found it necessary to remove the shifter from the transmission while we were dropping the transmission out. The shifter would not clear the transmission tunnel opening.
7. The T-56 bellhousing is easy to remove with the transmission out of the way. In some applications you can remove the bell and transmission as a unit.
8. The stock clutch assembly is removed next, along with the factory flywheel. This is a good time to examine how the clutch wore and if there are any issues that may adversely affect the McLeod installation, such as bellhousing alignment.
9. The stock GM flywheel sports heat cracking and discoloration. This indicates clutch slippage and a good amount of abuse.
10. While the flywheel is removed, it’s a good time to check for rear main seal and oil pan leakage. These one-piece rear main seals are easy to replace. If you have an older small- or big-block Chevy with the two-piece rear main seal, replacement becomes complicated.
11. The factory hydraulic slave cylinder and lines will be removed and replaced. We’re opting for the McLeod hydraulic clutch package for this clutch replacement.
12. The old clutch pilot bearing is removed next using a slide hammer puller, as shown. Pilot bearings and bushings can be stubborn to get out. If yours won’t come out, use a cold chisel to split it in half. Be careful not to damage the crankshaft.
13. The flywheel mating surface should be checked for scoring and dressed with a file, as shown. The file cleans up irregular surfaces, allowing the flywheel to sit square and flush on the crank. If there are irregular contact surfaces, you risk runout and the resulting clutch chatter or vibration.
14. The new clutch pilot bushing is installed using a deep-well socket, which comes in handy if you don’t have an installation tool. And no, we do not condone tool abuse. We also recommend the use of a clutch pilot bearing instead of a bushing.
15. The McLeod Super Street Pro clutch and flywheel package comes in a nice, complete kit, which provides everything you’re going to need. This is a nice dual-friction clutch with both organic and metallic friction material for smooth operation and a solid connection between the engine and driveline.
16. The flywheel and clutch pressure plate bolts get high-strength thread locker for heavy-duty applications 3/8-inch to 1-inch (10mm to 25mm) bolt.
17. The flywheel-to-crankshaft bolts are torqued in one-third values in a star pattern to a total of 60 ft-lb. Make sure the flywheel is seated squarely against the crank flange.
18. The flywheel face is cleaned with brake cleaner, which is an excellent degreaser and decontaminant. Use a lint-free tack cloth for surface wipe down.
19. The McLeod Super Street Pro clutch disc is a dual-friction disc with two types of friction material: organic and metallic for good street/strip performance. Here, Gary positions the clutch alignment tool provided in the kit to get the disc lined up perfectly with the pilot bushing.
20. Gary positions the pressure plate with the clutch disc and alignment tool. The bolts are hand-threaded for security before applying torque.
21. The clutch pressure plate bolts are snugged down in a star pattern slowly until all are seated. Once all the bolts are seated, they are torqued in a star pattern in one-third values to 35 ft-lb. Once tightened, they are checked again. Don’t forget to apply a thread locker to the bolt threads prior to installation.
22. The bellhousing is installed next. Once all the bolts have been snugged down they will be torqued to 25 ft-lb.
23. We’re going with the McLeod hydraulic clutch slave cylinder and release bearing, which is suggested for this application because it is designed specifically for the Super Street Pro clutch. It is also fully adjustable by using the McLeod-provided shims.
24. Gary measures the distance from the bellhousing opening to the clutch diaphragm. This gives him some idea of the distance from the slave/release bearing to the diaphragm.
25. With the previous measurement in mind, Gary checks the distance from the transmission front face to the release bearing, which should be close to what we had earlier. The release bearing is constant-duty cycle, meaning it spins all the time. It should be solid against the clutch diaphragm where there is constant pressure, but not to where the clutch is released, causing clutch slippage.
26. McLeod provides these adjustment shims, which give the release bearing proper depth into the clutch diaphragm.
27. Gary muscles the T-56 into place at the bellhousing, making sure the release bearing has the proper depth into the clutch. The bolts are installed and torqued to 25 ft-lb.
28. Once the shifter and hydraulic line are connected, the driveshaft is reinstalled. When you reinstall the driveshaft in a conventional U-bolt-style pinion yoke, never apply too much torque to the nuts. Run these guys down to where the U-bolt is seated and snug the nuts. When you overtighten the nuts, you can crush the bearing cups, which causes binding.
Photos by Jim Smart