Clutch installation, how to and what NOT to do!!!

[c4c5specialist]

Hi there,
Well, after many emails and PMs, we think its time to lay out the basic dos and donts about clutch installation on c5 and c6.

Aftermarket clutches, why would you NOT install one?
Well, basically, installed height. You see, the actual height of the fingers on the pressure plate from the clutch flywheel are CRITICAL to how the clutch feels when you push the pedal down. Its not that the aftermarket doesnt have the performance, they have great clamping force. Some clutch discs can also be made of different materials so that they are less subject to fade and sponginess.
In the 3 pictures below, you will see an aftermarket high performance clutch in YELLOW. The number written on it is the actual installed height of the fingers away from the flywheel surface. Below and to the right in the picture is a stock 2004 clutch, LS1.

The next one is a stock 2004 ZO6 clutch, which has a flat flywheel.

The third one is a stock LS7 clutch, which has a stepped flywheel. Even though it is a different type of design, the installed height remains consistant.

As you can see, even though the yellow clutch bolts in without a problem, the fingers are about .200 lower and therefore further away from the throwout/slave assembly.

This translates into a very abrupt engagement and virtually NO pedal progression.
Yet, it does provide excellent clamping force in higher horsepower applications.
This illustrates the fact that any aftermarket clutch will give DIFFERENT feel.

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[c4c5specialist]

Now, installation of the flywheel/clutch assembly is NOT as simple as bolting them in and driving away.

Every single manual equipped Generation 3 or 4 small block is fine tuned for vibrations and harmonics.
The factory does this by using BALANCING PINS in either the harmonic balancer, the flywheel or BOTH.

Now, it is NOT that the clutch assemblies are not balanced, they are.
The differences in manufacturing tolerances of the engines make it necessary to use this process for better vibration control.

YOU MUST UNDER ALL CIRCUMSTANCES remove the old balancing pin/pins from the flywheel, if they are there.
A simple check of the outside circumference of the flywheel will tell you if you have them. They must be installed in the EXACT same location as on the old flywheel. You can use the alignment hole in the center of the flywheel as an index mark, as seen in the first picture.

Then, as seen in the second picture, using a pin punch, tap the pins OUT of the old flywheel.

Install them into the new flywheel and retain using Loctite 272 on both sides.

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[c4c5specialist]

Now, YOU MUST replace the pilot bearing EVERY SINGLE TIME you replace a clutch.

They do fail and MUST be replace to avoid having a hard shifting condition and other issues.

Below is a picture of a failed bearing and a new one.

This particular one was replaced because the failure caused the input shaft to continue spinning when the clutch was depressed and a vibration was felt at ALL ENGINE SPEEDS.

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[c4c5specialist]

Fastener torque is CRITICAL, as is proper cleanliness.

Make sure you absolutely clean the crankshaft mating surface of all old loctite and contamination.

Assure that the mating surface on the flywheel is completely burr free.

Then, using the torque sequence below.

Coat all 6 bolts with Loctite 242 Medium strength and torque in 3 steps.

15 ft lbs

37 ft lbs

74 ft lbs is your final step.

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[c4c5specialist]

The pressure plate torque is equally important, to avoid distorting the pressure plate and creating chatter.

MAKE SURE YOU CLEAN THE FLYWHEEL AND PRESSURE PLATE WITH BRAKECLEANER!!!! DO NOT USE BRAKECLEANER ON THE CLUTCH FRICTION DISC!!!!

Align up the drive plate using a clutch pilot alignment tool.

Using the diagram below, torque the plate evenly over 4 increments to 52 ft lbs. DO NOT tighten one side while the other stays away from the flywheel.

I prefer 12, 24, 40 and 52 for the final torque. LOCTITE is not used on these fasteners.

Using a clutch alignment tool is very important given the alignment of the torque tube on installation so it is easy and doesnt damage the pilot bearing as you slide the driveline to meet the clutch.

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[c4c5specialist]

Clutch fluid today is GM part number 88958860. This should be flushed out every 2 years/24000 regardless of usage, per a revised service recommendation from GM.

The container is what is pictured below. USE THE ENTIRE BOTTLE, DO NOT SAVE IT!!!! It only has a 2 week life span once the seal is broken.

If you have aftermarket headers, HEAT is a problem.
Using a few heat insulating wraps have helped those with headers.

JUST REMEMBER EVERY SINGLE CLUTCH PLATE IS NOT PERFECTLY FLAT. THEY MUST BED IN.

That being said, a bit of chatter for up to 5000 miles is considered NORMAL, even when taking delivery of a new C6

See the other stickys in the c5 technical section for further information.

If there are any questions, please put them in a separate post.

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