HT1663WB

Hello, After a spirited drive, the clutch in my 2001 Z06 feels like the travel is reduced to about halfway, clutch pedal also feels stiffer. After normal driving the pedal quickly returns to normal. Fluid is clean, Vette has 45,000 miles on it. Only mods are VRB 2 and short throw shifter. It doesnt some to mess with performance any ideas?

Thanks, Bill

racebum

known issue with all c5s

was improved a bit in 2004

there is no fix without changing things.

neutron82

replace the clutch with an aftermarket unit and be done with it... also install a remote bleeder, new slave, inspect the torque tube couplers, etc

racebum

be careful if you do. some cars were hot balanced at the factory by counterweighting the flywheel making a hybrid internal/external balance engine. the manual c5 is very sensitive to vibration and thus why some required it.

if you just replace the clutch without checking the counterblance it will probably work but if it vibrates you are in trouble if you didn't mark where the OE flywheel was positioned.

going aftermarket means you also get stuck with aftermarket companies that may or may not feel and fit correct. the ls7 clutch won't stick on a stockish c5z but gets the same way as the ls6 clutch if you up the power

some guys have had luck using a tick master on the stock clutch since it moves WAY more fluid and is less likely to stick. the drawback? a stiffer pedal

neutron82

all good points above that should be taken into consideration... on the flip side I don't see anywhere near the amount of stories with aftermarket clutches causing a vibration as there are stories of stock clutches sticking to the floor, seems... like one appears every other day... I was lucky and didn't have any added weights on my balancer or flywheel, installed an act twin disc and all my issues went away... before that I tried a tick master and flushing it out completely the proper way with expensive fluid and still no dice

HT1663WB

Thanks for the replies. Will it hurt anything just leaving it the way it is? There doesnt seem to be any change in performance. I've owned the Z for about 5 years. I bought it with
just over 42k on the odemeter it now has 45k.

neutron82

you can leave it alone if you don't mind driving like granny all the time

73Corvette

What changes did they make in 2004 to make the clutch more reliable?

HT1663WB

It doesn't seem to bother the shifting. I can still run through the gears quick, spin the tires through 1st and 2nd with a healthy chirp into 3rd. I've had it on the track in Millville a few times no shifting issues. I had a base 2000 Vette MN6 that did not do it. I managed a 12.9 out of the 2000.

racebum

master had a slightly larger fluid moving capacity. there is a reducer in the master cylinder that's there to limit driveline shock. GM designed this clutch in this way to keep warranty costs down. two schools of thought on what causes this and they revolve around the self adjusting pressure plate and the master cylinder not being able to move enough fluid

the tick master moves a LOT more fluid than stock and has fixed this issue for some

my c5z does the same and it's 100% stock. by 3rd gear i notice it if i WOT from stop. i can still shift but you can tell what's going on

if hp goes up AT ALL from stock it only gets worse.

c5blackvett

You over heated your clutch? Never drive hard for to long. (ie. not to many hard shifts with out a cool down period.)

I am repairing mine now...

See the drill out section in below sections.
But you have to tear down to get the slave.
See
http://www.superchevy.com/how-to/eng...ally-speaking/

http://www.torcavettes.com/tech/ClutchHydraulics.htm

racebum

it's hp and traction related. bump up another 50hp and start running 12.4s around 115-116 and you will begin having issue. aim for 11s and the stock clutch with have some major problems and eventually fail

this is also why the c6z clutch is so popular for bolt on cars. make 350-400whp, it works dandy

mike venth

I made a copy of this information from the CF some time back, and will be doing this to my 01 (stock)coupe next month.....might help??

CLEANING AND REPLACING CLUTCH FLUID-INCREASING AIR FLOW
However, what is stated here will help extend the life of the clutch by keeping the clutch cooler and the fluid cleaner for much longer than any other method. This is primarily meant for those of us with stock clutches but will apply to all the aftermarket clutches as well. We have heard of many people that have put clutches in their vehicle when it may not have been necessary or many feel it is a mandatory upgrade with more power.

On our shop car we have a heads and cam C6 z06 with 585RWHP and 535RWTQ and 82K miles STOCK clutch from new and the car is driven like it is stolen, daily. The car has some drag racing time on it at the track but it is mostly thrashed on the street and road coursed as much as time and the budget allow. We have NEVER had the pedal stick to the floor and it takes about 5K miles for the fluid to change color let alone turn dark.

Drag racing does play havoc on a clutch but hopefully this will get those that are apprehensive out there to beat the tar out of their cars like they should be, it’s good for them!! It has been our experience that the 2 worst GM V8 vehicles out there for having issues with clutches are the GTO and the F-bodies. I would like to point out one thing that they have in common: They do not have an "exhaust" for clutch debris and heat. The back of the bell housing does not have vents like the Corvette and especially the C6. The 2 C6 vents are about 2" by 3/4" just beneath the clutch and in the back of the bell housing whereas the C5 was about 1/3 the size. The late model Camaro has a large vent roughly equivalent to the C6 size.

I mention all of this as an important backdrop that we will come back to shortly and I will try to tie it all together.

Even though this is a LONG write up IN SHORT it will only help even if you aren't have any issues.

I tried to illustrate with my kindergarten drawing ability Check out the clutch airflow pic at the bottom.

-Bleed the clutch line
For many of us are familiar with Ranger's articles about using a turkey baster to draw out dirty fluid and then replenish with clean the fluid.

This helps, however it is not the solution for the larger issue, you will still continue to get filth in the clutch and reservoir.

Please understand I am extremely grateful for his contributions to the corvette community. Ranger sent the fluid to a lab to analyze what the dark substance was in the fluid and established that it was clutch material. Without this important piece of info we would have much less knowledge about this system. THANK YOU RANGER!!

As you USE the clutch you consume it and where does the debris go? As the clutch material is flung around within the bell housing the material gets past a seal into the slave cylinder and then the hydraulic system the fluid is contaminated and begins to darken. If allowed to worsen you eventually will have a sticking pedal and lose hydraulics. In most cases not permanent but often at the most inopportune times. It is best to address this as early as possible so you do not have permanent issues with the stock slave.

We are not sure but it seems likely that damage may be caused to the slave cylinder by the clutch particles embedding between the bore and piston of the slave. Catch it before its too late. Naturally a clutch should give off the most debris upon break-in.

The factory system moves a very small amount of fluid in a line from the reservoir to the slave, fore and aft. Naturally the most contaminants would be at the point of entry into the system, not just the reservoir two feet away. Bleeding the system like a brake or any other hydraulic system until the fluid is clear would rejuvenate and minimize the contaminants.

A remote bleeder is nice and convenient but not all of us are willing or able to put a remote bleeder in or quite honestly I don’t know if you can even get one installed without tearing the torque tube and clutch out. So what can we do that is not too labor intensive and wont cost much? Or How can we optimize this system and make it last? Whether its the basic STOCK clutch setup or a rather expensive aftermarket clutch this should only help. We are going to tell you how we do it in the car without too much labor.

The easiest way that we have found is to pull the intake manifold for the C5 and C6 Corvettes. We have ported hundreds of manifolds so we have become proficient at pulling intake manifolds. (Total time to clean head ports and put it back on about 45min.) This will allow one to lay in and across the engine bay. With your head right at the firewall with a 9mm combination wrench and a light just barely have enough room to see the port, pop off the rubber cap (leave it off) and open it while someone else is depressing the clutch pedal. Bleed it just like a brake system, one person (A) holds pedal, the other (B) opens the port till fluid pours out and then closes, (A) pumps pedal till firm again and then repeat till fluid is clear, 3-12 cycles. Remember to check the reservoir! Refill it so you do not get any air in the line. Earlier F bodies and GTOs may be accessible from under the car and may not require pulling the intake manifold.

-Open front of the bell housing by removing the plastic panels.
There are 2 black plastic panels that cover the front side of the bell housing. The driver side has a small 3” panel held in place by 1-10mm bolt. The passenger side panel surrounds where the starter engages the flywheel. Disconnect battery; remove the 2- 15mm bolts and push the starter forward enough to pull out plastic panel. Before you reinstall the starter you can benefit from this wide open space. Check out the next step, Compressed air.

Total time will be between 10min and 1hr depending on stock exhaust manifold or headers and adjoining piping and space restraints and if on a lift or on the ground.

I would imagine that the panels were put in there to keep things from getting into the bell housing but the irony could be what was meant to protect the clutch hurt the longevity of it. The Driver side is shielded by the oil filter and the starter on the passenger side. It is quite amazing the amount of air moved by the clutch at idle from the “exhaust” ports of the bell housing, imagine what it would be in CFM@155mph 7k rpm. Ever heard of Smokey Yunicks flywheel supercharger?

Opening the front side of the bell housing is a crucial part of keeping things cleaner and cooler within the clutch. By allowing the front side of the bell housing to ingest airflow we now have a cross flow of air coming in and out of the bell housing and the faster we go the more volume of air through, like a radiator. With greater volume of high velocity air the clutch debris is expelled much more quickly rather than staying in the bell housing longer like the stock stagnant closed-front-entry (or it doesn’t exit but through a tiny hole like earlier Fbodies and GTOs). On our C6Z we even “ported” the “exhaust” side of the bell housing to even more aid in getting the airflow out. Furthermore, after about 7K miles we again cleaned it there was very little debris in the clutch and bell housing area and the fluid was in great shape too.
We feel that this is conclusive that it does keep the clutch much cleaner and cooler. What happens to a radiator when you block its airflow?

One more thing to mention about the GTOs and Fbodies: It has been our experience that the Heat and the clutch debris can very quickly ruin your fun. A few years back we had a ‘05 80K mile GTO with about 390RWHP and bolton’s, stock clutch. The vehicle was at a road course event and as the vehicle heated up it would lose hydraulics and not even be able to execute a gear shift by the end of a lap. We would have to draw out the DIRTY fluid and replace it every lap. (It is unknown how large a role the heat played it is difficult to test independently. When both sides of the bell housing are open it seems that it is no longer an issue.) Now looking back upon those experiences I know we could have resolved or at least greatly extended the proper functioning of the clutch. Since GTOs and earlier Fbodies do not have “exhausts” on their bell housings I would like to machine a few passages in there and see what happens......Now we have done the aforementioned methods to said vehicles and it has helped rather significantly but they NEED is the “exhaust” side opened up. When you take a look at the bigger picture you can see that it needs both clean high speed air in and high speed air out, just like an engine. Having only one side of it is merely half the battle.

-Use Compressed air and brake clean to blow out bell housing
Now that the panels are off you can get in there with a compressed air probe and blow out all the crevices of the clutch. We have been in there for over 10 minutes still finding more areas that blow out clouds or clutch debris. When you think you’ve blown it out enough keeping going. Then rotate the motor over with a breaker bar and do it again till there is no more clutch debris coming out. Next take 2-3 cans of brake clean and spray it all through anywhere you can. Wear a respirator and have some fans going in a well ventilated area; this is not good stuff to breathe in. Reassemble it and go beat the **** out of it.

We have a customer with a 30K mi 600RWHP C6Z that began to have some clutch slippage. We opened up the front side blew out and cleaned out the bell housing and has yet to have the problem again. One thing to consider is the contact surface of the disc and flywheel. If there is a boatload of dust in there, the surface has been compromised. The grip integrity of a clean surface has changed. Now it doesn't lay all the dust out evenly either so there is an even better chance that you will develop hot spots on the flywheel if one area slips on its own dust and another area grabs. Slowly we began to see how one thing leans on another, heat and dust, dust and heat.