MFranke

Ok, I've had my '88 auto since '93 and have since put over 120K miles on it. I am new to the 928 community and the forums, and I wish I had visited earlier because there are so many great folks posting here.

The '88 S4 has been very reliable compared to our other cars. Though, my anxiety went up when I started reading about torque shaft creep and thrust bearing failure, so I decided to inspect mine.

I lowered the exhaust - what a PITA considering I am probably the first to break these connections in over 20 years. I used heat and cold on the air line - finally got it.

Anyway, the flex plate had zero deflection. This is probably the first check in the cars life. I left well enough alone and buttoned it back up (first though I blew the acorn shells and other debris out of the torque tube). I left out the back two bolts. Thanks to Dwayne and all the other contributing posters for hints like this!

The message of this thread is that not all 928s have this flex plate pressure issue... at least it appears mine does not. Am I missing something? Mine is an on and off daily driver, with some occasional fun, but I don't race it.

Bertrand Daoust

Cool!

But I think this is the first one I've seen with that kind of mileage and no preload on the flex plate!

928mac

Awesome but I have to ask just to be sure.
You loosened off the pinch bolt right, loosened it so that the splines could move in the clamp if you pried the flex plate?

Then you need to see how much you can move the crank.
I used a pry bar being very careful not to damage or crack any aluminum.
I don't remember the spec off hand.

The reason I mentioned the above is because if it goes wrong, you dont get time to turn it off before the engine becomes a boat anchor.
So I have heard and never experienced, thank god.

The next 2 pics are how much mine moved when I loosened the bolt with 92,000 kilometers on it.
1st pic of splines before I loosened the bolt
2nd pic with less splines showing, (after pinch bolt loosened) verifies how hard it was pushing the crank




See how close my crank was to touching the block



You are not suppose to see brass so I just caught it in time.


This is not to scare you, just to educate you.

Brad

Landseer

It should be easy to take it back apart to check the endplay.

FredR

No has ever said all examples are/will be effected by this- it is a crap shoot plain and simple. Most examples that fail seem to do so around the 40k to 60k mile range but that is no barometer.

Sad to say in reality there is no seat of the pants advance warning it is happening. You either check and mitigate or throw the dice and hope. Plain and simple.

Regards

Fred

MainePorsche

I would put an auxiliary clamp on such as the Pklamp at least. You could go with Constatntine's clamp, though much more involved.
My flexplate had absorbed some tension without any endplay when I first checked it.
With the Pklamp I've had no tension on three re-chechecks after a total of 35 k miles.

MFranke

Thank you for the encouragement to check the end-play regardless of what the flex plate is doing. You are right and I need to do this.

The only thing I found out on this inspection this weekend is that, based on the flex plate check, the thrust bearing may not be seeing any significant abnormal pressure. Reading all the posts, I expected to see at least some plate bow - seemed like all 928s would have it. Seeing no plate bowing with a straight edge, I had left the clamp alone, figuring maybe it is locked on there pretty good. I wasn't sure that I'd be able to get that same joint tightness on retorque without using the green locktite that I've seen some folks using. I need to probably get some of that.

Dealing with the exhaust was the PITA, frozen and broken exhaust system bolts etc., and is behind me now. Leaving the two bolts off the end of the housing will help me big time when I go to work it next time. First though I need to figure out how to deal with the clamp at rear end of the tube ... how to get to it, etc. I've read that it needs to be loosened too as part of the torque shaft reset.

With the wealth of info this community has shared, I am just successfully coming off of some needed but time-intensive DIY summer projects with this car: 134a conversion, with new(used) rear blower and o-ring refresh (ugh); vacuum bladder refresh for center and footwell flaps; replaced the original rear wheel bearings (they were still in decent shape but I had time so I did it... B-90 works great); installed missing vibration dampers in the caliper pistons; sound system refresh with the Alpine ktp-445U (fits great under the cover where the stock amp fits); plus a bunch of other miscellaneous repair and refresh. The car runs strong, but I think next up for me is an intake, hose and fuel line refresh.

I came upon this torque tube issue and figured I'd better look at it. I've stayed pretty consistent on the thicker engine oils per the manual, so I hope that has helped too, but I will still check end-play before moving to the intake job.

1988 S4 Auto; Silver Metallic / Black

Adamant1971

Mine had its first check last year. 165,000 km's and 0 pressure released. I put a pklamp on at that time. 170,000 km's now and going to check it again.

docmirror

Um - I don't think I'm alone in advising you to take proactive steps to resolve this. You haven't really checked the migration until you've measured the end play with a gauge. This requires that you loosen the front clamp, and at that time, I strongly suggest you put the better clamp on it.

I hope you are right, but this is not an area where you should do half of the job. Loosen the pinch bolt, pry the crank all the way back, then set the dial gauge to zero with some preload, then pry the crank forward. You will likely hear a small 'thunk' as the crank moves on the thrust bearing. Read off the measurement and decide if it's within spec or at least close. Then put the Pklamp on, and check it again in a few thou miles.

MFranke

Ok - I finally got around to measuring crank end-play on the '88 (169K miles) and my recent '87 (71K miles).

I released the 88's clamp probably for the first time in its 25 years. I got 0.4 mm release, so the flex plate must have had some minor deflection, which was not apparent when I measured a few months back using a straight-edge. I measured the 88's end-play and got ~0.20-0.26 mm. I measured it numerous times, and it was slightly different each time, so I just recorded the range.

For comparison purposes, the '87 (71K miles) released a lot more, 1.65mm, but tighter end-play landing within 0.15-0.22mm. I'm not sure why the spline release on the '87 was so much more than the '88, considering the 87 has 100K less miles. However, the end-play difference makes sense.

Nevertheless, I am comforted by these measurements and will check them periodically when I have the cars up. I left the two rearmost bell-housing bolts out per Dwayne's sage advice. I painted one of the splines white and I torqued the factory clamp bolt to 65 ftlbs. If I see movement in the future i will consider a P-Klamp, but I am passing on it for now.