DannyGT

Hi everybody!

I might have a 1990 928 GT on hand for purchase. The car has a 5 speed manual gearbox.

My main question is about the dreaded trust bearing failure that the automatic versions have so much problems with. The way I understand it and looking at schematics of how the clutch and flywheel are put together with the prop shaft, there should not be any such issue with these manual gearbox 928s.

Is this the correct assumption? If anybody can show me a better drawing or pictures to show me why the manuals does not have this problem, I would appreciate this a lot.

What else is there to look out for on these cars. I know this is a tall order to ask but given the car has about 100K miles on it, something is probably going to fail soon. I have seen the car briefly once and will have a closer inspection soon.The car is a Euro version I believe. From Germany.

Thanks

Jason89s4

There are no TBF (thrust bearing failure) issues with manual vehicles. Your reading of the operation is correct. (FYI all GTs are 5 spd)
I believe the 90 has the PSD limited slip system. I’m not familiar with the system, as I don’t have it, but I certainly have seen many posts about getting it properly sorted. Others can chime in on that.

JBT3

Danny - going to try and upload an inspection guide for you. Hopefully this works. This is from @worf928 one of the most knowledgeable 928 mechanics in the country. Wish I had it when I was searching.

edit: attachment removed at author’s request.

928 GT R

This

jcorenman

Danny, 100K miles on these cars is nothing, any failures are much more likely due to a lack of maintenance than mileage.

As mentioned, 1990 was the first year for the PSD differential lock. If neglected (for example, the fluid never changed), then the small hydraulic pump can seize from moisture accumulation. A warning on the digi-dash indicates this, so it is not a "hidden" problem. A question for the seller should be whether any warnings or messages appear when the key is switched on. A 60-second video of the dash display should answer that. (It takes 10-20 seconds for the warning to appear if the PSD pump cannot build pressure).

Where are you located?

Good luck with your purchase, I hope all goes well.

DannyGT

? I dont understand.

DannyGT

Thank you all for the advice.

PSD will be under heavy observation both dash and behaviour on the road. Quite an interesting device. I can see the problems with this. Location of the servo pump unit. Why is it not in the spare wheel well? Tuning of the pump system. Tuning of the actuator on the case and adjustment on the case with correct pressure on the LSD discs. I always loved the LSD diffs. This takes it to a new level.

I am quite "educated on these cars as they have been my great passion among sports cars. Have never wrenched on one but have plenty of experience on lots of other cars. Love wrenching and "getting to know the beast." For me it is a major part of the whole experience.

Location is Norway. So a bit of the beaten track.

karl ruiter

Members generally chime in to form the text
this
thread
is worthless
without
pictures

Basically our way of begging for photos

DannyGT

I will make sure the photos are plentiful if the deal goes through.

Michael Benno

1990 GT is a great year car. Cant wait to see it

PSD FYI:

928 GT R

DannyGT

I love it!

Cheburator

Firstly, Congrats on the new purchase!

Secondly...

Contrary to popular belief, 928 5-spds could also suffer from TBF! When you start the car, most drivers instinctively press the clutch. The 928 has a pull-to-disengage clutch. The diaphragm spring is quite hefty, particularly on the S4 as it's a single disc design. As you pull on the crank, there is hardly any oil pressure on the thrust bearing. I have done 4 manual engines, all around 120-160k miles and all had copper showing on one side of the TBF... Three of these engines had decent service records with Porsche main agents and were in excellent health overall for the mileage. And as you would expect, the TB wear was on the opposite side of where you would find wear on an Auto...

I am not scaremongering, just stating a fact. Euro cars - like my GTS 5spd, GT and S4 5spd have no clutch starter inhibitor switches. so you can always start your new GT just in neutral and with clutch engaged, thus prolonging the life of the TB well into the future.

P.S. Btw, all 4 thrust bearings had life left in them and were not catastrophic, but had clear signs of proper wear unlike the other 4 plain bearings which were as good as brand new...

P.S. 1 In addition, being a GT - it must have seen higher RPMs than an Auto through it's life, perhaps it's prudent to budget time for conrod bearings replacement. a Glyco set is about EUR100 and you can do engine mounts, pan gasket while in there and it really isn't difficult if you know how to turn a set of spanners.

khalloudy

I have seen some 1990 cars come with the LSD rather than PSD. I guess this is market dependent. The only way to verify is to check the build code whether the car has a PSD or LSD.. that would be east. Also note that the 1990 dash harness has both plugs to support either build… this is very specific to that model year.

DannyGT

Thanks for all the good tips. The seller is away right now but returning soon. Will know more about the deal in a few days.