[Steve]

I have searched in this forum for things related to go old clutch slip. There is a lot of discussion on stock and modified flywheels, but I have not found (yet) much about the clutch slip.



My clutch started slipping this weekend at the PCA OCR AX/DE. There are no other symptoms at this time. I drove back to Pasadena and under normal street driving it is fine. It slips when I get on it hard in first or second.

I assume from my experience from less sophisticated cars that this is a simple matter of replacing a worn out clutch plate and throw out bearing. But, after reading several threads here I get the sense that it may be a larger problem, yes no?



I would be grateful for any illuminations on this subject.



Cheers

Steve Patrick

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[flash]

it really depends on the condition of the flywheel - there are 2 main questions involved



1- did you wait too long and score the surface of either the flywheel or pressure plate?



2 - is the reboud of the DMF action diminished beyond spec?



either of these being yes will indicate a need for replacement of the appropriate part or parts



beyond that, the fork bearings and rear main seal may be in line for replacement, depending on their condition



the bolts that hold the pressure plate and the ones that hold the flywheel are not reusable

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[Steve]

Okay thanks so it needs to be looked at. This is a job at I don't think I want to do or do I? Is it a lot of work?

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[flash]

it's not an ugly job, but not a simple one either - it really it depends on how set up you are (there are some special tools you will need), and what kind of mechanic you are - it's way more than most would do, but somewhat simple for others



it takes me about 4 hours to do one on this car, but i'm pretty well set up, with tons of tools, space and light, and i've been doing this kind of thing for entirely too long



while i really hate wrenching, there really are few jobs i wouldn't do myself, and this one is one of the bigger jobs on the list, but certainly not insurmountable



that probably didn't help much

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[Steve]

It helped fine, thanks.



I have been doing my own wrenching on 911s, 912s, 356s and Alfas for way to long also.



I did do the timing and balance belt on this car and have done several clutches before so I guess I am okay with this.



At least you don't have to pull the motor.



What are the special tools?

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[flash]

flywheel lock, short reach torque wrench that will accurately measure 17 lb/ft, and socket and long ratchet for the crank bolt



the rest of the tools are pretty standard stuff



the instructions in the shop manual are pretty good

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[Steve]

I bought the lock for the belt job so that I have and it will be nice to have a shorter torque wrench.



I guess I will get under there and do this. <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />



Thanks again Bob

No really, thanks

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[tloof]

Surely you guys have an impact wrench? There is no need for the flywheel lock when an impact wrench is used to remove & install the pressure plate bolts & flywheel bolts (when doing a clutch job), and crank bolt (when doing a front seal change job & belt change job). Buying the special flywheel lock is a waste of money if you have an impact wrench in my opinion!!



Also, changing the clutch on the 968 is the easiest clutch job on any vehicle I have ever seen since you don't have to remove a tranny from behind the engine like 99% of all vehicles. Hell, changing all the belts & seals up front is WAY more work in my opinion!

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[flash]

yes, you do need one - torque specs are very important - you can't apply correct torque to any of the pressure plate bolts without the flywheel lock in place to hold the flywheel still

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[S_Cal968]

Sure an impact is good for disassembly, however assembly is another story. Using an impact for installation may over stress the bolts by going past the torque spec.

Also, it's imperitive to torque the pressure plate bolts evenly in a cross-pattern.

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[cdtscout]

[quote name='Steve' post='31337' date='Feb 22 2007, 05:10 PM']I bought the lock for the belt job so that I have and it will be nice to have a shorter torque wrench.



I guess I will get under there and do this. <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />



Thanks again Bob

No really, thanks[/quote]



Steve,

I just finished relplacing my flywheel, pressure plate, disc and all the other associated stuff on my daily driver 968. I agree with most on this board...this is a fairly straight forward repair. I had the most difficulty with replacing the rear main seal...tried the various fabrication tools...but ended up buying a specific tool for the job. I can't tell you how long it took me since I worked on the car in small time segments...Kids, job...the usual.



Anyway, dig in have fun and take your time.



Craig

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[tloof]

The initial tightening down of the pressure plate in a cross-pattern is easily done without having to lock the flywheel up to about 10-15 ft-lbs or so. The final torqueing of the bolts can be done with a reasonably high quality impact wrench that has a max setting of 250 ft-lbs and 10 intermediate settings that allow close to about 25 ft-lb increments. I have tested my impact wrench against my torque wrenches & it is usually very close in torque value in comparison, and any additional 12-15 ft-lb value somewhere in between the 25 ft lb increments can generally be achieved with a very short burst of air pressure that is regulated down lower to the impact wrench. What I am talking about here is really using the impact wrench only for the flywheel and crank bolts that require alot more than 50 ft-lbs of torque and where it is difficult to stop the crank from rotating when attempting to torque the bolts. For values up to 50 ft-lbs on smaller bolts a simple torque wrench works better, as well as any bolts that you don't have the problem with rotation of a shaft when trying to tighten them. The larger crank & flywheel bolts don't need to be that precise in torque value as listed by the factory (+/- 12 ft-lbs is OK), especially the flywheel bolts since you should always use red locktite on them (which requires a propane torch to get the red locktite to melt before you can get them to loosen again).

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[flash]

have you done a clutch in this car before? it's really hard to keep the flywheel from rotating to torque the pressure plate bolts - i'm pretty lazy, always looking for a faster way to do something, and no stranger to a wrench, and i couldn't figure out a way to do it



the torque setting for the pressure plate bolts is 17 ft/lbs - no way you are going to get that with an impact gun



i can tell you from unfortunate experience that 15 does not get it, and 25 is too much - the cross pattern is crucial, and it takes at least 3 full rotations of the flywheel to achieve good torque across all 9 of the bolts



where did you get the tolerances on torque? - the workshop manual states 40 first stage and 90 second stage for the crank to flywheel bolts - i don't see any plus or minus tolerances - i would expect maybe a variance of 2-3 lbs would be acceptable, but that's it

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[rustech]

[quote name='flash' post='32519' date='Mar 15 2007, 01:02 PM']have you done a clutch in this car before? it's really hard to keep the flywheel from rotating to torque the pressure plate bolts - i'm pretty lazy, always looking for a faster way to do something, and no stranger to a wrench, and i couldn't figure out a way to do it[/quote]



Couldn't you just throw a large socket wrench on the crank and hold it to stop it from turning?

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[flash]

hmmm - i suppose you could find some way to either wedge it in there, or get somebody to hold it still, though that still falses the torque - it's just far enough away though to be difficult, and i only have 2 hands, and it takes at least 3 to do that (one on the head of the tri-square to make sure it doesn't slip out, one on the torque wrench, and one on the other wrench)



lol - or you could just do it right

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[tloof]

Perhaps I'm confused here! How does the flywheel lock help you when torqueing the flywheel bolts or pressure plate bolts since the flywheel lock bolts to the starter hole location on the bell housing which is off the engine when changing the clutch? The only thing the flywheel lock helps for torqueing from what I can see is the front crank bolt, which isn't all that critical to get the exact torque value! (which is where the impact wrench is OK to use)



The 17 ft-lb torque value that the pressure plate bolts require should't cause the crankshaft to rotate against the compression cycle of one of the cylinders if you keep the spark plugs in the engine! (it never has on any engine I have ever changed a clutch on). If so a second set of hands would easily be able to hold the flywheel from rotating by gripping the starter ring area of the flywheel.



Yes the factory service manual doesn't give any +/- torque values on the flywheel bolts, but that doesn't mean that it isn't OK to be +/- 10 ft'lbs or so (especially when red locktite is used on the bolts to prevent them from ever coming loose on their own).



By the way, what is the best clutch and pressure plate that those of you have used to replace the factory setup when a new clutch is needed? (brand, cost, and supplier to get it from)

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[flash]

it hold the flywheel still so you can torque the bolts



it seems that you haven't been in there to do one of these yourself - is that right?



i would suggest doing one of these, and then you'll quickly see what the problems are



it's not a hard job, but you need the right tools

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[tsj9197]

on a 968 you don't have to remove the entire bellhousing to access the clutch.



there is an access panel the comes off after you get the exhaust out of the way. you don't have to drop the tranny and shift the torque tube back like a 944.



i'd say it's the easiest clutch job i've ever done.



much easier than my 83 944 that i had to do the job twice in 2 days because someone put the wrong pressure plate in the clutch kit.

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[Steve]

Does some one out there know where I can find a XZN Star type socket for removing the clutch pressure plate that is not make out of Chinese cheese?

I got one screw loose and stared then next when this tool striped. Funny I went over to the bench and got a file and it cut like butter. I filed it down past most of the twisted and striped crap and almost tried again until I felt it going again. I got this on line from a recommended source. It looks like most of the XZN Star type sockets you find on line are the same type. Any help??

<img src="/forum/images/smilies/968/mad.gif" class="smilie" alt="" />

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[flash]

ouch - that sucks - yes, those things will shred if you don't have it seated down squarely in the head of the bolt - a real pain - i took to tapping them home on each one before cracking them - it didn't take much for it to get cock-eyed and want to turn

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