camboinc

Fellow shark lovers,

my mechanic is ready to drop a freshened motor into my 87 S4. I have purchased a rebuilt TT from 928 specialists. My mechanic posed this question to me today so I am asking it here.

Is there a shim pack required for the install of the TT to the motor on an 87 S4?

He helped Jack Riffle with his earlier model 928S (cant recall the year- 84 perhaps?) and recalled a shim pack being utilized.

87 and newer owners, please chime in if ya gots tha 411.


thanks everyone !

jon928se

In a word NO.

Make sure that the your mechanic tightens the clamp bolt on the front clamp dead last to avoid preloading the flex plate. Also use a new clamp bolt and tighten to 10% above factory spec - 66lbsft IIRC.

blown 87

Black Sea RD

This really will not have any effect on the clamps clamping ability. Our tests have shown the OE clamp itself does not clamp as tightly after repeated use. The new pinch bolt and torquing to a higher setting does not do anything.

The higher torque setting actually came as step two of a solution from allegedly Porsche to stop the drive shaft pulling out from the clamp. The first step was to put in a new flexplate and attached clamp. That part, which is expensive, was conveniently forgotten in later talk about this topic.

The reason there is not a shim pack used in the MY 87 TT is the driveshaft does not have the area needed to place the shims, circlip and washer at the front. This practice was also discontinued by Porsche due to problems in setting them up corretly resulting in some customer cars suffering thrust bearing failure (TBF) of their engines. At least what we could piece together from our look into the whole TBF thing.

Hope that helps,
Constantine

heinrich

say .... how about a less stiff flex plate?

Vilhuer

Isn't there possibility to use shims on '85-87 tubes? IIRR '88 is first year where its not possible. In any case it debends on what TT version 928 Intl send you. If it was correct style I would use shims.

Mark Anderson

We offer both style torque tubes. If you request the version with the longer shaft you can use the factory shims and prevent thrust bearing failures. We have the shims in stock if you need them but I'm sure 928 Specialist can provide those as well.

Bill Ball

As Mark mentions, we chose to use the longer shaft and the shims and retainer with circlip when replacing a broken TT shaft in a 91 recently. Just exactly how to setup the shims with the drivetrain in the car is a bit of an art. My reading of the WSM is that there is supposed to be a tiny (0.3mm? IIRC) of clearance between the shims and the back of the flexplate. We were able to get the shims with retainer and circlip on from the engine side of the flywheel with a small circlip plier, although there isn't a lot of room to work. So, you could go that route or you could install the later shaft and use other techniques to fix the clamp in place.

I've heard that the groove for the shim retainer circlip continued to be present on shafts for a couple of years, but I haven't confirmed that directly.

camboinc

juicy! thanks for all the responses. much appreciated!

Black Sea RD

Well I might as well chime in and say that our new clamp will work with both old and new driveshaft versions, stops the migration of the driveshaft in the front flexplate clamp, will probably outlast the car and is relatively inexpensive. The best time to put one in is when the TT is out of the car. The main reason we developed this is to help stop the dreaded TBF from happening to anymore 928 automatics.

No measuring, no guessing and hoping you got it right. Porsche did stop the use of the shims for a reason.

Hate being a self promoter, but...

Constantine

camboinc

Constantine-
i believe the tt is back in the car but the motor is out. your clamp... can you tell me more ? how much? etc?

thanks!!

brian

Vilhuer

Go with Constantine's clamp especially if you have newer version of the shaft. No question about it. There are few threads about it in archives.

https://rennlist.com/forums/928-forum/189614-tbf-clamp-fix-offer-long.html
https://rennlist.com/forums/928-forum/269954-tbf-fix-clamps-have-arrived.html
https://rennlist.com/forums/928-forum/312706-928-flywheel-clamps-batch-2-a.html

All shafts which are 25mm diameter along their full lenght should be this long type and allow use of shims. When exactly they were changed to most part 28mm diameter shorter version is somewhat open question. IIRR factory yearly documents say it was in '88 MY. At the beginning or some time during MY, don't know.