guys, ive spent ALOT of time tracking down this problem. The problem is exactly as described many times here even though I have a c5. Basically at the top of 3rd WOT it'll get spongy and after the end of the run in 4th, the pedal is pretty much at the floor and it has to be pumped. Ill tell you the step by step processes i've done to isolate the problem.

First time this happened w/ my stock clutch I had long tubes. I took it to my buddy at GM and he put a slave in it. Problem persisted. After that I had him put a ls6 clutch in. Problem gone for 6 months but came back. At that time I was pretty frustrated and it was winter. I tore it down and put a new slave and master in it. I also put a remote bleeder on it and bled the fluid for the 1000th time and put high temp racing brake fluid in it (MOTUL?) I also put my stock exhaust back on to eliminate the headers and heat as an issue. As an added heat reduction I took a 10AN braided line and slit it down the length of the hose and also wrapped it in high temp reflective fabric tape I drilled the orifice to 1/8" Problem persisted. To further eliminate heat, i went WOT after the car was stone cold out of garage, no way for heat to build fast enough to be an issue, same problem.

So at that point I had replaced: Slave, master, eliminated heat, fluid and air. Leaving Clutch assembly. WHen i tore it down over winter to put in a new slave, the disk and PP looked BRAND new w/ no bluing of the flywheel. Ive never had a slipping issue so it left the Pressure plate as the culprit. At this point im 99% confident the problem is caused by the GM PP Design. THe only there I see tha holds water based on all of my testing is a warpage of the PP fingers causing pulsation of the TO bearing and aeriating the fluid in the slave/master. I can somewhat further back that up based on a slight pedal vibration I felt when i had my foot on the clutch pedal at a higher rpm but not disengaging the clutch.

I just put in an ls7 clutch w/ a new slave but exsisting master. No clutch pedal sticking yet and there is little to no pedal pulsation right now. I will be keeping a note of pedal pulsation and any sticking that may occur. If this were to happen again, it'd probably be about 4000 miles from now just like the ls6 clutch was, but I hope not. Being that the only things replaced to solve the problem last time (pre LS7 clutch) was replacing the clutch (not hydraulics) i'd say its a PP in most cases for most of us. Not those who experience low RPM pedal problems, just us high RPM Drag and road racers.

BTW< i know the ls7 clutch has temporarily fixed the sticking pedal I experience because I can duplicate it at will going to redline in 3rd/4th.

Dave

 

ya i really think its the pressure plate.
one thing is i have always had my pressure plate resurfaced. and have not put a shim in it untill now.
moving it back like that might have been a problem even with the adjustable master.

i would say if my problems doesnt get fixed with this last attempt then i would be getting a new flywheel, but this is my last attempt as a T400 will go in its place if it doesnt work.
might down the road try it again with a mcloud twin disk, but until i can afford a clutch that expensive, ill have to take the short road.

 

insulated the line today and it seems to of helped. The pedal still gets mushy but it hasnt stuck yet (only tested it once and only took it to 3rd gear). I will try it on the freeway later and see how it does. I have not blead the system yet either. I just mity vac'd it.

 

Is there a heavy duty PP that you can buy that wont warp?

 

I have a LUK Pro Gold setup right now with aluminum flywheel and their PP. Is that PP more durable than the GM one?

 

i also had the pedal to the floor problem.

shield the line REALLY well, do the drill mod, and install the McCloed master. problem SOLVED

 

not for me it didnt although I did not buy the Mcleod master just have intalled 2 different 02 masters.

 

i drilled a 1inch hole in bottom of my bellhousing to properly measure the air gap.we need @.060 gap with the clutch pushed in.if not the clutch can drag on shift making them more diffucult and heating them up.my 2 cents but i can shift at 6500 all day long now.used many shims to get it there.

 

intresting but refer to my other post in your other thread. BTW.. can you post pictures of this? Your hole that is.

 

I am now smelling clutch at WOT so the clutch is spinning and I think the Pressure plate is the culprate. We will see this following week.

 

This is probably the reasoning for the relocation of the PP in the LS2/LS7 setup.

 

Ive had this problem also. Replaced the hydrylics and still the same problem. Put a spec 3 in it and that fixed it. They last about 22,000 to 26,000 miles then the problem comes back. I think its the pressure plate weakening because it gets worse gradually. I'm going to try a spec 5 next time. I can feel my cutch starting to do it now and I'm on my 3rd one at 74,000 miles. It seems to have a problem with sustained high rpm and the pressure plat and disc are the only thing spinning. If it were the hydrolics I would think it would stick at all rpms.

 

My stock clutch/hydrolics I still question. I have 400rwhp, and my clutch will grab suprisingly hard, and wont ever slip. But, if I get on it (and NEVER SHIFT), the clutch becomes mushy. And if I do shift, it will be completely gone/stick to the floor.

To me I think its a combination of weak hydrolics and other things. Any ideas?

 

get the air bubbles out. i'd try that first. use a mity vac.

 

I had this problem for the first time today - at 18.5k miles. This pisses me off to no end. I got stuck in heavy traffic. The pos 4 cyl factory clutch is tolerating the engine pretty much the same as always.


I knew nothing of this before and thank goodness, I just happened to try and pull it back up. Got me home without a tow ok.

 

I can tell you this: a long style clutch with unequal finger heights WILL cause that same problem.

Back in the day, all diaphram clutches would go overcenter and stick to the floor, but I would assume that is fixed today. It would be interesing to see of 10 or 20 thou shims between the pressure plate and flywheel had any effect ...

 

My clutch return spring has been gone for two years, and no problems using the McLoed MC with Ram clutch.

 

That is exactly what I found with my long style clutch. We had to take it apart because an adjuster got screwed up and didn't get it shimmed right when we put it back together. The clutch would work fine with the engine off and still work at idle or low RPM, but impossible to shift at high RPM because of no pedal. I had a hard time believing it because it seems like the fluid going past the piston in the MC should end up on the floor of the car, but it didn't. BTW, it did this with two McLeod cylinders. Fixing the clutch fixed the problem.

 

I am installing my new clutch assembly tommarow (Friday).

 

so far, my clutch feels AWSOME!!! It is a spec stage 3 with a fidanza aluminum flywheel. I am 60 miles into the break in period so I have not floored it or anything to see if it still sticks. I used the shim that came with the kit that goes behind the slave. The pedal feel is so nice. Not too hard but much stiffer than stock. It feels like I have a strong clutch and not some import clutch. It does chatter a little right now but I am under the impression that will dissapate throughout the break in period. So far so good though (knock on wood).