MiamiDave

Long story short: I had my LS1 clutch/slave replaced under warranty-Clutch pedal sticking to the floor on upshifts for months. They replaced it at 14K miles with stock LS1 gear.

About 16K I went with CCW Big Street package to include Michelin 335/30-18's Pilot Sports out back, and at 16.5K went with H/C making max 423/385 RWHP/TQ.

Now I'm at 20K miles and just replaced the MP/S 335's in great condition (already sold) to go with a stickier competion tire-which grab great with no spin from rolling on it in 1st (even in this "freezing" -75 degree weather

Car has NEVER been speed/powershifted or forced to endure high rpm dragstrip launches with any tire. Factory MN6/3.42's. If I wanted to come out quick from a stop I would just slip the clutch or bog it and let the gear pull me out and than gradually go WOT.

Two things I noticed immediately with the comp. tires:
1st gear no spin whatsoever-quick shifts into 2nd also no spin (wasn't much spin in 2nd with the MP/S 335's-but they spun like mad through first below 80 degree weather). I also had a quick sensation of clutch and flywheel mating-w/o the tires breaking loose one bit.

So, today I try my first holeshot with the new comp tires (75 degree weather, tires 32 lbs, were not heated or even cleaned). I planned on trying to walk her out rapidly at about 3-3500 rpms to see how they gripped. I started taking her out, got it rolling, eased up on the clutch releaseing it and the revs flash up to 5K and the car rolls merrily along no faster. The trans feels disjointed from the drivetrain as I clutch in and take it out of 1st, and than back into neutral

Clutch mushy on way up-no springiness...Crap! Heavy clutch smell! Well, I put back into 2nd (wow-tranny is still there), ease the clutch back up and pull away.

I drive it cautiously a bit, gears engage no problem, clutch feels fine (pedal pressure even lighter)-overall much better. I do a few quick flat punches in 1st/2nd-no spin of rear tires and clutch grabs solid. It seems like there was never a problem-except it shifts better and feels lighter...? I'm scared to do another holeshot though...

So, one big WTF!!!

servohead

I dunno man. Your just running too much frickin power through that clutch. It seems that through all of my reading on this forum and from my posts concerning my stock clutch that the stocker is pretty weak. On the other hand I have seen people say that they had a stock clutch last for some time with a H/C package. Not sure why yours is acting up, but I wouldn't be suprised at the slipping that your experiencing. I'm sorry to hear about your troubles though. Just going to have to upgrade! You'll get it right man!

BLOWNZO6

You cannot put that torque through a stock LS1 clutch. Z06 clutch is a little more forgiving, but it is time for you to upgrade.

curtbriggs

I have a 1999 coupe, Z51, full Corsa pace car system, Hypertech, big K&N, so nothing special. I've had the car since new. I tried a 4000 rpm launch with the EMT's at around 8000 miles, got allot of wheel spin. I then changed to the Z06 Supercar size tires all around and tried another 4000 rpm launch got nothing but clutch slip, just as you described. A month or so later I tried another launch, same results. I've 30,000 miles on the car and don't abuse the clutch with the exception of the above. I figured it was time for a stronger clutch. All this time the clutch has worked perfectly in normal driving, no sticking issues. The other day I tried another launch and much to my surprise, NO CLUTCH SLIP. BTSOOM!!! The two times the clutch slipped, I caught it immediately to save the clutch. I've been drag racing big engine cars and bikes for over fifty years so I've allot of clutch time. BTW all four attempts to launch were on the same strip of pavement, same air pressure, however the tread on the 295's is now on the thin side.

MiamiDave

I'm glad to see others have had a similar problem-especially normal driving vrs. the hard launch. I'll try it again today at -3K with some less slip. I guess I'll consider upgrading in the "near" future.

It's pretty easy to hemorrage money with these damned things

IFLUBYU

Too much power and too much grip for that clutch. If they replaced your hydraulics with stock LS1 stuff, that is probably the heart of the issues you are seeing now. You got it replaced under warranty, so you aren't out anything there. At your power level a stock LS6 clutch probably wouldn't last long either if you are going to drag race with any frequency. You can baby that one and it will last a bit, but you should start planning on saving for a performance clutch.

Good Luck!

MiamiDave

Played with it some (same conditions as yesterday and it felt grippy, bogging the car during a few back to back 2000, 2500, 2700 launches.

Since it grabbed and transferred power to the wheels/bogged the engine, I'll just let it ride untill it looses it's grip at WOT. I'm planning on one of the aluminum flywheel medium clutch combos in the future...

Dope

Curious, which tire did you go with? Toyo RA-1s? I plan on running 335/30/18 and 275/35/18 RA-1s in the spring, I'm just wondering how you like em.

Oh, and as far as the topic, when you put that much power into that much traction with the stock clutch, it's gonna be pretty much hit or miss. It's only going to get worse though.

Dope

MiamiDave

305/35 Nitto RII Extremes. They are not a drag tire, just soft compound & hard sidewall. Are those Toyos a Comp tire?

Dope

Yes. Very similar. R-compound, made in similar sizes (275/40/17, 275/35/18, 305/35/18, 335/30/18), same treadwear (100), etc.

I assumed Toyo because you said you previously had 335/30/18, which Toyo makes, but Nitto only has the little 305.

Dope

5 Liter Eater

The real test for the clutch would be to put it into 6th doing like 40 MPH and nail it. This puts more load on the clutch than just nailing it in 1st of 2nd. If the revs come up independent of vehicle speed it is on it's way out.

It's a shame they didn't give you LC6 components when they did the warranty job. I thought that was standard procedure.

There is an adjustment that can be made on the PP to take into account disk wear that can give you some more clamping force but it's probably worth a new clutch. Either a Z06 or a LUK Pro Gold.

see5

More power and more traction and you found the weak link.

MiamiDave

I looked online and the Toyo RA-1's comp tires I saw had a treadware rating of 40 compared to the Nitto 100-which to me is significant since I do a lot of driving lately and the temps here are consisitently higher than, well....anywhere

The 305 is smaller and slightly taller, which may help some rubbing issues but the treadware patch looks to be about 10 inches. Here I though stretching it out would give me a wider contact patch, but now I don't know. It may have been a tire designed for lower pressures than 32 or a lot more camber...

MiamiDave

[QUOTE=5 Liter Eater]The real test for the clutch would be to put it into 6th doing like 40 MPH and nail it. This puts more load on the clutch than just nailing it in 1st of 2nd. If the revs come up independent of vehicle speed it is on it's way outQUOTE]

That's partially true as a test when a clutch is completely shot-but realize that lugging the car when it's only making low hp/tq at low revs and comparing a sticky tire vs. an engine making 300+ hp/rwtq (at 3,000+ rpms) going 0-5 miles an hour-the heat and power mixed with a sticky tire will cause the clutch "weak link" to give up...

Anyway, it still grabs and holds through 1-5 gears at various rpms and loads-I'll just have to watch my holeshots...