[ctsv154]

This is what is going on. New slave, new master, when I shift at red line my clutch pedal will only come back up off the floor about an inch and I have to pump it back up and I can not get it into another gear until its pumped up again. If I shift at 4-5k, everything is fine. Any idea? New hydraulics leaves me to think that i may have a problem with the LS7 pressure plate but when the pedal is down I cant get it into another gear, that means the pressure plate is still clamped which leads me to believe its a hydraulic problem. I dont get it.

Yes I bled it.

 

[darkman]

I have looked at the Service Manual section on clutch problems. Assuming you have eliminated hydraulics (which I would think you have) the only external candidates remaining involve the clutch pedal - either a missing return spring and/or worn pedal bushings.

All other possibilities are internal including (as you observed) the pressure plate and all the other components such as pilot bearing, throw out bearing, clutch disc (warpage), flywheel, splines, etc.

 

[945liter]

This is what is going on. New slave, new master, when I shift at red line my clutch pedal will only come back up off the floor about an inch and I have to pump it back up and I can not get it into another gear until its pumped up again. If I shift at 4-5k, everything is fine. Any idea? New hydraulics leaves me to think that i may have a problem with the LS7 pressure plate but when the pedal is down I cant get it into another gear, that means the pressure plate is still clamped which leads me to believe its a hydraulic problem. I dont get it.

Yes I bled it.

LOL thats the problem im having im hating life it all happend after a 1hr dyno tune session i have an ls7 slave in there too but im about to change it, i can got WOT 1st to 2nd @ 7k no problem after that i have to pump and physically lift the pedal. I can also go WOT thru all the gears as long as i shift @ 5k i got a new master im going to install soon i checked the line to see if it had a restrictor like Fbodys to do the drill mod but i did not see any.

Im going to do the master and the slave at the same time and pray. Im hating this i haven't been able to race my car since ive cammed it.:banghead:

 

[darkman]

I did some poking around other forums on this subject and have come across a number of reports of problems with the LS7 clutch setup. It seems to be limited to those: (a) with, or at least claiming, high horsepower numbers (450+ rwhp); (b) LS7 clutches were not new but not high mileage; and (c) WOT with high rpm shifts (6.5-7.0k). This may, or may not, indicate some sort of limitation with the LS7 clutch since you never know all the circumstances leading to such reports.

 

[ctsv154]

Thanks darkman

 

[ctsv154]

LOL thats the problem im having im hating life it all happend after a 1hr dyno tune session i have an ls7 slave in there too but im about to change it, i can got WOT 1st to 2nd @ 7k no problem after that i have to pump and physically lift the pedal. I can also go WOT thru all the gears as long as i shift @ 5k i got a new master im going to install soon i checked the line to see if it had a restrictor like Fbodys to do the drill mod but i did not see any.

Im going to do the master and the slave at the same time and pray. Im hating this i haven't been able to race my car since ive cammed it.:banghead:

Well I replaced both the master and the slave and still have a problem. Good luck! I guess I'll be buying a pressure plate and disk soon. Just gotta figure out which one!

 

[d0nindp]

When the dealer replaced my clutch they had this problem. It took them 3 days to get if fixed. The master and slave were replaced. Stock 06 V with something like 25k miles on it at the time. They even made several calls to the place that dealership mechanics call when they have problems. I believe they finally fixed it by bleeding the clutch lines MANY times. Several times they thought they had it fixed and then on a test drive the clutch pedal would stick and they had to go back and bleed it again.

Not sure if that's the problem you guys have, perhaps it's something to check?

 

[ctsv154]

I'll keep bleeding then as well. Thats a lot easier than pull the trans out again!

 

[lollygagger8]

Sunuva!! This makes me want to stick with the stock clutch!!

Hope you get this figured out man......please let us know if the extra bleeding helps

 

[ctsv154]

Will do. Plan on playing with it today sometime as long as the rain holds out.

 

[PISNUOFF]

Give it time and it'll do it at progressively lower rpm's. Your pressure plate is worn out. My LS7 did the same thing last year. You can bleed it a million times and every which way you can think of and it won't help, I know, I tried!!! Finally, I replaced ONLY the disc and PP (BTW - they come as a balanced assembly) and problem fixed. Mine wore out after by about 6 track days. When this one wears out I have a lead on a twin disk with a lightweight flywheel for $1,400 total, that is claimed to handle more power than I'll ever have in my V.

 

[ctsv154]

Hmm.... I'll be looking into a good pressure plate that fits the LS7 flywheel. I know they are more because its a recessed surface but I'm not buying another flywheel.

 

[The Tony Show]

Have you tried the "Drill mod" yet? Very popular with high HP Corvette and F-Body owners.

Basically, the fluid line going into the master cylinder has a restriction in them that can cause fluid starvation at high rpm and a stuck pedal. Many people think that this is the reason pressure plates seem to wear out so fast in LSx cars.

I'm not personally endorsing it, but it might be worth doing before you throw down for a new PP- can't hurt, right?

Read all about it HERE (scroll down to step 16).

 

[ctsv154]

Thanks

 

[bpitas]

When the clutch is working, where is the release point of the clutch? I know you didn't drive it for a while, so it might be hard to remember, but do you think the clutch engages lower on the pedal now than it did? If not, than I wouldn't think the problem is bleed related. If you have a bleeding problem it'll engage closer to the floor and may be slow to come back up past that because there won't be enough pressure to return the pedal to the upright position. But if it works fine most of the time and only screws up at high RPM I'd suspect that the input shaft collar is scored so the throwout bearing is catching up on the shaft in a particular location at higher RPMs when things heat up or something.

My low clutch problem was a bubble in either the master or slave, and it worked itself out by driving over the local bumpy roads (no amount of manual bleeding or mighty-vaccing helped) but yours sounds like something else... I'd check the clutch return springs first since it's such a pain to pull the tranny. That looks pretty easy in the manual, although the manual makes *everything* sound easy.
Good luck!

 

[ctsv154]

The clutch works fine except when I hit 6k plus. The throwout can not catch on the input shaft because of the way it is made. Clutch return is still in one piece.

 

[The Tony Show]

Plus the clutch return spring isn't meant to actually raise the pedal- it's just for feel. There's plenty of guys who have had the spring break and fall out, and their pedal still comes back up fine.

I think it's one of two things- either the pressure plate is weak and being held in by the centrifugal loads at high rpm, or the fluid line orifice is causing cavitation at high rpm and needs to be drilled out.

 

[PISNUOFF]

The clutch works fine except when I hit 6k plus. The throwout can not catch on the input shaft because of the way it is made. Clutch return is still in one piece.

???????


Also, a new LS7 disc and pressure plate is only about $300

 

[ctsv154]

I'll take a picture when I get home so you can see what I'm talking about. I'm not going to install another LS7 pressure plate if its going to fail in 5k miles.

 

[PISNUOFF]

Thanks, but I know what it looks like. I don't see how it could catch on the trans input shaft. I've had my new LS7 PP in for 6K miles and 3 hours of on-track time and still as good as new. I thought for sure it'd be done by now also. PM me if you want a hookup on a $1400 twin disc.