I just finished breaking in my new Spec stage2 clutch and relized that something in my drivetrain is STILL slipping somewhere. I know my old clutch was shot-- when I replaced it, I checked the thickness of the friction plate with a dial caliper and confirmed that it was worn out (and also saturated with oil from an oilpan gasket leak which is now fixed). So logically the new clutch should stop the slipping problem, and it hasn't, its just reduced it slightly. The clutch install and break-in went fine, I had a few smaller problems during installation but got everything straightened out. Its like I can still do burnouts, but I cant get the tires to chirp in between gears anymore, and if I floor it in 6th on the expressway the rpms fly up almost to redline and the car barely accelerates.

So now I'm confused, what else could be slipping? Maybe the clutchpacks in the differential? The car does have 110k on it, maybe they're worn out. The T56 was rebuilt last year, but I'm pretty sure manual transmissions don't slip when there's something wrong... they just grind. So I think the only thing else it could be is the differential clutches slipping.

I'm still pretty unsure about it, or how to even diagnose the problem, so I'm very open to suggestions or help at this point.

 

I see no mention of resurfacing or replacing the flywheel. Was this done or did you put a brand new clutch on your old flywheel?
The clutch packs in your diff are to distribute torque evenly to the axles. If they give out then one wheel receives all torque. There is no way bad clutches in the diff would act like a slipping clutch.

 

Your new clutch is slipping. Nothing else that'll slip in the driveline like that. I'm wondering if you have an alignment or adjustment problem somewhere thats preventing your from full pressure across the clutch. My stock clutch is pretty whipped, it'll slip if you really hammer it on an upshift, but it'll hold the higher gears on the highway at WOT - you must have something pretty far off if you new clutch is worse than that already - and if you're slipping on the highway at cruise, you're defintely gonna need to consider resurfacing the flywheel, you may have heated and chewed that up some.

 

SS_RRR - Thanks for clarifying that for me about the clutches in the differential. As for the flywheel, I installed a brand new OEM flywheel, so there was no need for resurfacing. I was going to have the old one resurfaced and use it again, but I wasn't sure how many times it had been resurfaced in the past by the previous owner and didnt wanna take a chance at there being too much material already removed.

acammer - I used the clutch alignment tool that came with the new clutch when I installed it, and everything seemed to line up fine since the tranny slid right in. I also bled the clutch even though I didnt really need to. As for adjustment, I'm not sure what else there is to adjust-- I'm on a stock origonal master cylinder and a 1 year old stock slave cylinder (Long story: I had to drop my tranny to send it out to get rebuilt last year, in the meantime I took the clutch/flywheel out to fix a rear main seal leak, then when I put everything back together my old slave exploded when I forced the pedal down because I didnt engage the clutch fork properly), and there's no leaks in the system.

 

Hmmph... so strange, it certainly sounds like you covered all your bases. You don't have another leak thats contaminating the clutch somehow do you, maybe an leak above the bellhouse on the motor - like at the intake? If you're getting slip like you mention, its gotta be the clutch - anything else in the driveline wouldn't slip, it would just break.

I haven't had a 4th gen long enough to know, but other stick cars I've had/worked on, have had adjustments for pedal travel in the passenger compartment - any chance you might have such an adjustment, and its not returning the clutch to full engadged? I know we fought a clutch problems on my buddies VR4 and it ended up being a stupid adjustment right at the pedal. Just a thought.

 

How does the clutch pedal feel when you disengage the clutch? Does it feel smooth with even pedal resistance through the entire clutch pedal travel? You mentioned the old slave blew up because of not having the clutch fork engaged correctly, was the fork damaged when this happened? Could it be possible the fork was damaged and is not allowing the clutch to fully engage now?

 

acammer - actually for the first time in the 3 years ive owned the car, there's no leaks. When I first got the car it head the dreaded intake manifold oil leak at the back of the manifold. It was pretty slow though, atleast slow enough that it never effected my clutch. But I fixed it anyways, with new Felpro gaskets and ultra copper RTV at the front and rear of the manifold. When I put the new clutch in, the back of the block was bone dry. I guess all I can do is check the pedal for adjustment like you said, and maybe see if there's some sort of adjustment on the slave or master cylinder that I'm overlooking.

97pontta - The clutch pedal feels the same as it always had, even resistance throughout, and just a little tiny bit of play at the top of the stroke. I'm sure the clutchfork wasn't damaged though... I mean I dont think you can even hurt those things if you wanted to, its one heck of a solid chunk of steel which is probably why the slave cylinder puked first. The only issue I had with the fork was that the surface of the tips of the fork that pull on the throwout bearing looked worn down and cooked, maybe just an eigth of an inch or so. This forced the slave cylinder to push the fork just a little furthur than normal in order to fully disengage the new clutch, which in turn caused it to rub a bit on the spinning pressure plate. I answered to this by grinding about an eigth of an inch of the fork where it was hitting the pressure plate and the problem was solved. As to how this could be preventing the clutch from fully engaging is beyond me though, but at this point... who knows.

 

I agree the clutch fork is pretty stout but there is always the possibility it could cause a problem. It sounds like everything else in your setup is squared away so I would double check your clutch fork again as it is the one area that took some modifying to make work. I'm not implying that you need to remove it or separate the transmission, just maybe remove the slave and inspect that area to be sure there isn't something obvious causing your slipping problem.

 

I spent a pretty good amount of time under the car today, I took the slave cylinder off and took a very good look at the hydraulic system and clutch fork and all seems well. When the forks fully engaged with the slave unbolted there's a little bit of front-to-back play which tells me the fork isnt hung up and disengaging the throwout bearing or anything-- so that looked alright. The master and slave cylinder were fine, and there didnt appear to be any adjustment on the either one or the clutch pedal.

I also took the starter and inspection cover off and the back of the flywheel and inside of the bellhousing were bone dry, no oil at all. However I did notice that there's a new leak on the back of the intake manifold at the drivers side corner. It seemed slow, so I got a torque wrench on the rear intake manifold bolts and retorqued the loose ones back to 35ft/lbs.

I was completely out of answers until I thought about it-- when I was bolting the pressure plate to the flywheel, the torque specs in my haynes manual seemed completely odd: "15fl/lbs then rotate an additional 30 degrees". I remember torqueing them in and thinking "that's the dumbest things I've ever read". Especially since the torque wrench would 'click' at 15ft/lbs looooong before the pressure plate was touching the flywheel surface (the threads were fine, I even cleaned the bolts before I put them back in). Even with the "additional 30 degrees rotation" most of the bolts werent even tight enough to make the pressure plate touch the flywheel either. So basically I just improvised and snugged all 6 bolts until the 2 surfaces met.

My theory on this whole thing is that during the "500 mile clutch break-in period" when I couldn't floor my car, the 6 pressure plate bolts have been working themselves looser and putting a gap in between the flywheel and pressure plate preventing the clutch from fully engaging. I think the last thing I can try doing is pulling the tranny back and one at a time, remove the six pressure plate bolts, put blue threadlock on them and torque them in a lot tighter than I did before. Theyre hardened bolts and the flywheels iron, so unless I'm hanging off the wrench I shouldn't have to worry about stripping anything.

It makes sense that the torque spec in the Haynes manual didnt work since theyre for a stock LT1 clutch, and I'm sure whatever pressure plate comes in a Spec 2 clutch is heavier than stock. I'm assuming its a knock off LT4 plate or stronger. Either way it will require more torque to tighten down than a stock plate.

Sorry for the essay guys. I figured the best thing I could do is throw as much detail into here as I could with hopes that someone will call me out if I'm doin something wrong or keep giving me suggestions as you guys already have been. Thanks.

 

If you have any doubt that the pressure plate bolts are not tightened correctly I agree that they need checked right away. It would really suck to have something come loose and damage the new clutch, hydraulics or trans.

 

I had a Spec stage 3+, If I let out and let the clutch engage then floor it, The clutch would hold, but if I powered shifted, It would slip and go straight to the rev limiter, Never found out what the problem was, when I pulled the clutch, of course the flywheel and clutch showed signs of slippage, blue burnt marks. I am now installing a McCleod twin disk...

 

OP, where in IA are you at? im by Council bluffs.

 

Get this one figured out yet?

 

I believe that is for the v6/5spd. There should be a definate torque spec for the t-56 pressure plate to flywheel. I just finished my last week but cant remember what it was.