Speedtoys

If you really want it...go for it.

Its a -rare- condition, IMHO. go find the # of threads on thrust failure in the last 5yrs.

Tom. M

Depending on when the last oil change was, you can at least have them "change" the oil and cut open the filter. If there is an issue with the thrust bearing, then there will likely be something to see on the oil filter element. Might be a quick way to assess prior to purchase without doing the check and give you some comfort in purchasing. When you get it, you can then do a full check.

SecaBlue

Thanks... I had heard about checking the oil but not sure if just 3000km since the last oil change earlier this year is enough to show anything. 🤔

SecaBlue

Ha... True. You are not making it easy for me 😛

karl ruiter

I recently toasted a thrust bearing. Mine was an unusual case, perhaps, because I did it quickly by driving hard and manually shifting the auto with no clamp. Even so, here are a couple of points about mine:
-Good thrust bearing to destroyed thrust bearing was accomplished in ~20 miles.
-Endplay still looked reasonable.
-The bearing did not spin.
-It would have been very easy see by cutting into the filter-there was metal everywhere. In fact, no need to cut, just inverting and draining it showed the metal.
-Motor would start when cold but lockup when hot.

SecaBlue

Interesting. What miles were on your car when it happened? What engine?

karl ruiter

It was my '88S4, so the 5.0. Odometer failed at 60K so TMU, but about 100K, I would guess. I had checked it recently at about 0.005". My theory (maybe everyone's theory now, I don't know) is that this has to do with the drive shaft twisting and shortening under load. When it is short it slips back in the collar of the thrust plate and stays there so presses on the thrust bearing when it untwists. So romping on it, and manually shifting it did the trick right away. Luckily I knew exactly what had happened and shut it down right away and the engine seems to have been salvageable. I pulled up to a light and the engine died. When I tried to start it back up the motor would not spin. So it went back to check the battery connections. Not only were the wires tight, but they had become super hot from me trying to start it. So I knew the starter what trying hard but the motor was stuck. Towed it home and by the time I got there it was free again.

karl ruiter

Oh, and to clarify, you don not remove the exhaust manifolds from the motor. You unbolt the exhaust from the exhaust manifolds. 6 M8 bolts, easy to get to. Once you have done this job once, you can probably do it in two hours, counting jacking up the car and taking it back down again. Maybe one hour if you left the two rear bolts out of the cover the first time. And that is if you are on your back on the floor using a floor jack. For a reasonable shop with lifts and lights and well organized tools I don't see how they could possibly spend even four hours at it.

Constantine

Not as rare as automatic 928 owners would like to believe. Don't forget there is a broader 928 world out there than just on Rennlist.

Now advising any client with a 928 automatic, no matter the year, to first do a crankshaft end play check before doing any other maintenance directly after purchase.

Speedtoys

Yes, there is a wider world, but it's not insignificant here either. Likely a solid sampling of it.

FB 928 forums are not finding a lot either..if any that I've seen.

Not saying its NOT a problem, just saying I had a better chance of catching Dengue Fever mo ago, than a random auto 928 having this.

Constantine

Catching Dengue Fever only requires for you to be a human.

The main requirement for 928 engine TBF is for it to be an automatic.

So yes, a smaller number.

Speedtoys

DF, like TBF, requires the -right- set of circumstances, in the right order..and then even if exposed, 1 in 4 change you see ANY symptoms at all.

Ya...lots of automatics, not a small number at all...and yes, it can happen, to any auto 928, IN the right aligned set of circumstances, rather like Dengue.

Yet the online 928 world is NOT an auto hospital ward full of TBF patients.

Not saying don't check, but if THIS car is your unicorn, the odds are in your favor that it's just fine.

I've read more threads on significant 5spd "challenges", than TBF ones in my residency here.

SecaBlue

I love all the different feedback and experiences

Admittedly when I bought my '87 S4 a few years ago, I was completely unaware of the TBF and just bought it and drove it home 600km. It had 140K km and full Porsche service history in Sweden by one of the most competent Swedish Porsche mechanics (who personally owns the only 959 Sport in Sweden). So I was fairly confident it had been looked after. I sold it again though before driving it more... someone made an offer I could not refuse :P

My only reservations with this current prospective GTS car is the lack of any invoices or history prior to 2019. Yes, it has Porsche stamps up to 2001, with kms there being 78K, and 2019 being 113K. But then I also believe that IF they had found metal shavings in the last oil change, the current owner would not have kept driving it another 3000km to today. Hmmm.

Constantine

From my perspective, buying a 928 automatic without checking crankshaft endplay by a competent shop, not all of them are, is a gamble.

This after years of being contacted by owners/shops who have suffered such an event looking for guidance on what to do next.

If you can afford such a gamble, then purchase it.

FredR

Although there are no hard and fast rules regarding TBF those of us who have followed this issue with interest over the last 23 years have noted some commonalities, the main one being that when such happens it seemingly tends to do so when the mileage covered is in the range 60k km to 120km. The problem also seems to be more prevalent on the later model automatics with the 28mm drive shaft but it can happen on models with the 25mm drive shaft where Porsche dropped useage of the shims/locking washer assembly [a really dumb move].

I also suspect that models that are driven as they were meant to be driven are more vulnberable to this problem as are examples that are driven in hotter climes. Over here I noted 5 failures on a fleet of 30 vehicles- those numbers are not statistically relevant but if they were truly representative it would be deeply worrisome. Slippage of the front clamp has nothing to do with how the vhicle was maintained as there was no formal Porsche instruction for routine intervention.

Stop the clamp from slipping and the problems just do not seem to occur. When the clamp slips one of two things will invariably happen, either the 28mm drive shaft will shear just behind the splines or the thrust bearing acts like a disc brake and destroys the thrust bearing that typically seizes, spins in the journal and ultimately cracks the webbing in the crank case then for most examples that is game, set and match for that motor. A few examples have been recovered by those with special facilities and talents but generally speaking it is not a commercially viable procedure.

Purchasing a 928 automatic with no knowledge of these issues or the status of the proposed purchase is risky to say the very least. On the other hand experience tells us that if such is going to happen chances are it will likely have happened already so the frequency of such failures seen in the community can be expected to drop as the years pass and that does seem to be the case.