polcan

Hi all
1988 928 S4
I'm in the middle of TT TC bearings replacement ,( not to mention
intake refresh and powder coating at the same time) ,it is not
army of ONE job. Got TT off ,shaft out ,TC cover off, upon separating
TC cover torque convertor came out with it ,hope that will not cause any problems ,ones out it was easy to split them apart .
My question is :
I did not have at the end of my drive shaft( to Engine side) ether: circlip or
spacer or shims for preload of flex plate .WSM is pretty confusing in this matter . Should I have had those missing parts ?






all out in one piece





washers on cross member





engine end of my drive shaft with grove for circlip

James Bailey

Porsche stopped using the clip and washers....then people began having more problems with the clamp sliding and excessive preload on the flex plate which leads to thrust bearing failure... T B F much has been written about that !!

Chalkboss

As far as the washers or spacers go, I did not have any on my 87 either. As I read the WSM, if I remember correctly, it says to replace spacers in the same location if present. I read that IF as they were put in if needed. And also I think they were used to isolate vibration from the rest of the chassis. As long as you keep a few mm of space between the crossmember and mount you are fine.

At least that's my take.

Mrmerlin

your getting a couple of different answers about different parts.

As JB said The driveshaft does not have any clips like the early cars did.

Chalkboss is talking about the cross member to chassis shims.
The rear cross member to chassis might have shims to prevent loading the cross member,
these should be installed in the original position.

With the TC out you want to be careful installing it.

Since you have it out, it would be a good idea to replace the front pump O ring.
Use Dow Corning 111 on this O ring.

NOTE leave the gasket alone just wipe it off.
WHY because it will stick to one side and removing it will usually damage the part its stuck on, (think 16V cam tower gasket removal difficulty)
The gasket doesnt usually leak unless it is damaged.

NOTE make sure to put some Vaseline into the bronze bushing that the TC rear snout fits into,
so it wont seize when you start the engine.

NOTE call Greg Brown and ask him what parts he would change with the trans out of the car

GregBBRD

Although Porsche shows the shims, special washer, and circlip in PET, and the '84-'88 driveshafts remained longer with the circlip groove, none of the 4 speed vehicles were equipped with the travel limiting circlip and associated shiming.

While several people make clamps to limit flex plate preload, the addition of the circlip and special washer (along with the proper amount and thickness of shims) is the ultimate retention device to keep the flexplate from moving forward. This flexplate retention method works so well, that I retain the longer driveshaft with circlip groove in my custom 300M driveshafts!

Adding these pieces to an assembled vehicle is extremely difficult, due to the very limited access (through the flywheel) of the circlip groove (which is likely the reason the circlip, washer, and shims were not used in the 4 speed vehicles.)

However, when the vehicle is disassembled, simple measuring and calculation make the addition of the circlip, washer, and proper shims very straightforward. I would encourage anyone in the OP's position to add these parts and be done with any flexplate issues, forever. (I've been adding the pieces for about 20 years, when possible.)

There's a few tricks to accomplishing this task....if there is any interest, I'd be happy to provide the required knowledge.

OTR18WHEELER

I am interested in the tricks...
Although the loc tight method has worked well for me over the past two years, the next time I'm in there, I want to add the clip.
(Wifey knows why my rear tires didn't last 20k miles)

FredR

Excellent photo to demonst would think].rate how to drop the transaxle in one lump. We had a recent discussion about whether the unit can be dropped leaving the rear member in situ but when you see the job lot like this I would wonder why do it any other way?

Good luck with the refurb. As I remember when we did my TC bearings the unit itself has to come out to get at the rear bearing and probably the front one as well unless my memory of what we did is seriously skewed 10 years of grey matter degradation later.

I am still a member of the Loctite fraternity [No 2 in the world to use Earl's method as I remember] but if the minister of finance permits, in your situation with everything out on the deck I would be considering Constantine's excellent clamp very seriously.

I take it you undid the 6 bolts at the flexplate to flywheel? I had no problems breaking the loctited joint with the unit out of the car. It would be interesting to read about how you fared breaking this joint should you choose to do so [not really necessary I would think].

Regards

Fred

polcan

Hi all ,thx for replay ,yes I think droping whole unit as one is the way to go. I believe no aliment will be needed after assembly ,I did mark cross member position to body but it looks like fixed fit .
Ahhhhhhh 6 bolts to flex plate I used a impact gun (ahhhhhhhhhhhh don't scream ) ,had to remove
flex plate too, with bell housing all the way back to body (only about 1"clearance) drive shaft would not clear flex plate.

Greg
Plz share procedure how to measure and install shims .I.m going with super clamp but for piece of mind I want circlip and bushing in place (got spare drive shaft that has it )
Thx

Black Sea RD

The problem Porsche had with the circlip, bearing and washer set up was technicians were having problems correctly setting up the measurements needed between the flywheel and flex plate. They decided to stop using them in 1984. If the measurement is not set up correctly, TBF can visit the engine.

The Super Clamp was designed to be much easier to set up and use. If using it we do not recommend using anything else which could do more harm than good. It is a stand alone fix for this problem.

polcan

Just a couple more questions:
Can I put 3 bearings instead of 2 ? have spare bearing housing ,space them even with
vibration damper in between first 2 ?
Constantine clamp is perfect but with our $ dropping to **** i.m looking at $450 .00 CDN just for clamp.



I hope Greg is going to share some knowledge here ,much been discussed about TBF but none about
lack of preload causing it, no write ups about it !!!!!

GregBBRD

The procedure, with the entire drivetrain removed (or with the engine removed and the drivetrain still in the car) is pretty simple.

You need a very flat front flex plate to get good measurements. If your flexplate has a permanent bow, is warped, or has run out on the three wings, get another flexplate (928 International).

Assemble the entire torque tube and related pieces onto the transmission. (Torque tube onto transmission, front bell housing, flexplate attached to its flange. Install 3 of the thickest shims. Install the special washer that retains the flexplate circlip, along with the circlip.

Loosen up the rear pinch bolt at the transmission end. Pull the driveshaft all the way forward, so the driveshaft is forced up against the bolt. Apply some gentle pressure to keep the driveshaft forward and torque the bolt.

Measure the distance from the bell housing to the flexplate. Now measure the distance from the recess in the flywheel where the flexplate sits to the engine block.

Simply change shims until those two dimensions are the same.

Re-assemble with these shims. When everything is assembled amd torqued up, the flexplate will be perfectly flat and it will be impossible to pull the shaft rearward out of the flexplate, from this point forward (because of the shims, washer and circlip.)

You don't need any special clamp or any other magic. Early stock shims with circlip and washer, combined with the driveshaft that has the circlip groove. Done. Spend the money you were going to spend on whichever supplementary clamp you were going to buy somewhere where it will do some good.

Note that it is possible to measure what circlips are required and do this entire process, with everything installed in the car, although installing the circlip on the driveshaft, through the late automatic flywheel, requires some special skill and patience! At one point in time, I considered making up a special set of custom bent circlip pliers to make getting the circlip on easier, but just never got around to that task.

Constantine

Greg,

Why must you ridicule other products which can help stop TBF when you give your wisdom to the masses?

Let's have a complete discussion on your technique, which is also outlined in the 928 WSMs. The circlip, bearing and washers are not readily available. To set the proper distances you describe you must have the shims with different thicknesses to choose from, which many don't have. So some will default with a "good enough" mentality when trying to replicate this procedure at their home or shop which then sets them up for possible failure. Just like the Porsche field techs were doing just before Porsche, who initially developed this fussy procedure, finally abandoned itself.

Those with the newer 28mm drive shafts are out of luck since these drive shafts do not have the area needed to mount these pieces. Truthfully we dislike the 28mm drive shafts due to them being prone to shear failures.

So when we stood up new 25mm replacement drive shafts (about ten years ago) we made them with the groove and area needed for these parts just to give owners this option.

The Super Clamp works well, is easier to set and can be loosened and tightened when other maintenance is needed. We never considered or sold it as a "magical" solution, just one based on good ole mechanical principles. It is a solution used by many around the world and helps give them peace of mind when driving their 928 automatics. And it is not a money maker for us, trust me.

The other clamping solutions, to include using red Loctite, have also worked for people.

Constantine