Anyone ever heard of this? I called ACT the clutch company that makes the kit, and they'd never heard of such an issue.

I'm on an NA drivetrain, with a stock NA flywheel, but with a Large streetported S5 TII block. Stock turbo, custom front mount, running 7psi. RTEK 1.7 550/780cc injectors. 3" downpipe back.

When doing WOT pull in 3rd the clutch seems(I use seems, because that's what I think) to slip, but not the typical, soft, rev up without accelerating slip. It's a VIOLENT CHATTERING slip that shakes the whole car. It's pretty damn scary really.

Has anyone EVER heard of something like this?

Clutch is an ACT sprung 6-puck disc, with an Ebay pressure plate. Held 10psi of boost fine before the front mount, this is a new issue.

 

Are your sure your drive shaft u-joints are in good shape? What is awesome about this, is you can't simply replace them (well, unless you go my route and have a shop custom wizardy the **** so you can) without replacing the whole shaft.

Does the rear or middle of the car seem to shake more? sorry, "chatter"

 

Not the drive shaft. It is most definitely the clutch, and the car slightly revs up when doing this. And if i let go of the throttle it instantly stops and i can get back on it(90% anyways)

 

Does the clutch pedal have the correct amount of free play?
The more aggressive clutch material, the more chatter you'll encounter when the clutch is slipping.

 

Have had this clutch set up for a while and mever had issues until i went with a front mount and made a little more power

 

Could be the pressure plate not having enough clamping force for your newfound power

 

burnt facing on pressure plate and flywheel is notorious for a shudder on engage

probs needs a mild re-facing on both , including adjusting the flange face height accordingly

i would be looking close also at the straps on side of pressure plate
and perhaps a double check of the button center springs to see if one has torn itself slack

 

get a better clutch.

 

This. High/hot spots = shuddering. Could be either the pressure plate or the flywheel. Were they new/resurfaced prior to install?
I similarly looked for other issues to fix my shudder, but it just needed to come apart.
I'm skeptical that the eBay pressure plate since even stock clutches can handle that power level.

On a side note, 7 psi on a front mount should not produce more power than 10 psi on a top mount. So that probably isn't what is causing the problem.

 

You're clutch flywheel & disc is glazed. Happens when you slip clutch too much and it over heats.

 

I installed a clutch on my na in April and did not resurface the flywheel which had hot spots and now I'm definitely getting a chatter in reverse and sometimes in first.
That's what I get I guess.

 

My car gets a little chatter, which I don't mind.

But that's not the issue here. My issue is it happens when already in gear, engaged, mid way through a pull. Starts juddering, and shaking the whole car.

 

Had same issue as ^ on stock power and parts. Machined flywheel and new clutch, no chatter now.

 

Sounds like it's time to drop the trans....

 

^ change the pilot bearing, seal, and release bearing if you didn't last time. To save you from dropping the tranny again later. Be picky when inspecting stuff.

When having someone machine it, have them remove the pins and machine the same amount on the step where the pins are, so that the clamping force isn't affected (only NA's have the step on the stock flywheel). They should take the least amount needed to remove hot spots and make it all even (0 runout).

 

Update:

Bought a new 6 puck clutch, new PP, rated at 345ft lbs, resurfaced the flywheel, and torqued everything to spec.

Didn't change a thing. I can't even get to 2psi before the clutch starts chatter-slip-vibrating. I'm getting the SAME exact issue as before, with a completely different clutch, and PP.

Really need to tune this car ASAP, and I can't with this issue.

 

Next step is replacing the flywheel. Are you sure its not something in the trans?

 

Replaced trans as well

 

Counterweight? Doesn't that cause vibrations and what not if Mismatched with flywheels??

 

Same counterweight and flywheel since the beginning. Never had issues.

 

Is the clutch slave correct for the trans? Is it releasing completely including the pedal adjustment?

 

It's the same set up that I've always had. Never gave me issues before this

 

That means nothing, adjustment can get screwed up at anytime

 

Considering my clutch engagement point is like 3/8ths way up from the floor, and the last 1/4 of the pedal is just free air, do nothing space, I'd say that it's not my issue.

 

could be clutch "pump up"

does it happen immediately with everything over-night cold or does it kind of come with warming up?

had this on my old FC. If you pull "up" on the clutch pedal really hard it would release the trapped fluid and stop slipping. mine would also feel like the engagement point was kinda moving slowly upwards