Clutch slipping in 1st gear.

[adampecush]

This is not something that happened recently, and there is really nothing I can do about it right now since it is -20C and my car is sitting in an unheated shed likely encased in snow, but I was wondering if anybody had any insight...

I installed a new Spec 3+ clutch (on machined flywheel) in my car, which is currently running no more than 300 HP to the wheels. Back in fall, i was attempting some hard launches, and when trying to launch by slipping the clutch at 4k, the clutch slipped completely instead of the wheels spinning (with the pedal fully "out". Keep in mind that I've probably put around 1000 miles on the clutch. The clutch does not slip in any other gears either.

I have a suspicion that I may have to adjust the master cylinder as the clutch disengages near the top of the pedal travel; however, when I unhooked the pushrod from the pedal, I couldn't really pull it out any further.

Is this a case of
a) adjust the damn pedal,
b) clutch needs more breaking in, or
c) learn how to drive/don't slip the clutch on takeoff and 275 rears are too much.

I feel that a clutch reportedly capable of holding ~600 whp shouldn't slip like this...

Adam

 

[lewis15498]

Something is definitely wrong here, not just your driving, it should be broken in by now...

 

[adampecush]

i should add that I'm using a brand new slave cylinder but not a brand new master (master has 30k km). Prior to tearing my car apart, the old stock replacement clutch behaved the same way when launching, though I just assumed I was overpowering it. I suppose this points toward the master cylinder adjustment.

 

[theKnifeArtist]

Hmm, subscribed for info.
Only in 1st?
Maybe a LSD issue?

 

[Poodles]

4K is a bit high IMHO

 

[adampecush]

Hmm, subscribed for info.
Only in 1st?
Maybe a LSD issue?

rebuilt LSD.


no tires spinning whatsoever.

 

[adampecush]

4K is a bit high IMHO

if the clutch holds, it'll throw you back in your seat damn hard...

 

[IJ.]

Flywheel machined flat?

 

[Poodles]

Thinking backstep not machined? Only thing I can think of at this point...

 

[IJ.]

That's my guess, are they a puck clutch?

 

[Zumtizzle]

Maybe not enough step....

That's my guess, are they a puck clutch?

3+ is full face.

 

[Poodles]

Mine's a 6 puck, might be the issue as well.

 

[adampecush]

backstep was visually there, didn't personally measure it though.

edit: just checked with my machine shop and their literature recommended a 0.020" step, which is consistent with what I've read for our flywheels.

 

[Poodles]

Might just be too much for a full face clutch...

 

[adampecush]

on a clutch "supposedly" rated for 620 tq, it better not be...

I think master cylinder adjustment will be my first order of business

 

[Poodles]

That would be the first thing I'd look at as well. If you loosen the jam nut and you can't rotate the shaft by hand it probably has preload on it.

 

[GrimJack]

I launched my spec 3 way meaner than that, and it just grabbed on and spun the tires, so I doubt it's the capacity.

 

[Rajunz]

You should have free play in the clutch pedal before it engages. Sounds like your pedal is too tight. Mine did this when I first installed a new clutch. I was able to adjust it out.