SteveG

Spent the day doing the flex plate jive. '93 GTS with 68,880 miles. When I finally got the bugger exposed, sure enough with a straight edge, I could see the deflection toward the engine. Measured carefully, when released, she moved 1/8 inch and the straight edge was now flush. So Rennlist saved another engine. Everyone should check this on your A/T. I'm too lazy to do it, maybe when I retire, but is anyone keeping a log of these? It would be interesting to record, MY, miles, deflection. Or not. Just do it.

PorKen

The flexplate check is the second thing I'm going to do when I get my 86.5 home, after the timing belt system.

Bill Ball

1/8th (3 mm) is pretty much the standard deflection found whenever the flexplate is checked. Check again in a month or two. With any hard driving, it will be back to 2-3 mm.

tdelarm

So the question goes...how often should this be checked?

Bill Ball

Of course, there is no official schedule for this as Porsche doesn't recognize any issue excepting with incorrect transmission installs.

The following is just my opinion: If each time you check it, you get 2-3 mm, that seems to be an equilibrium point that does no harm. People who develop thrust bearing failure most often have 10+ mm of preload. Why? Who really knows, although we debate this from time to time. If 2-3 mm, release it and check crank endplay for a baseline. Check again in 6 months (that's assuming you drive regularly and the car is not a garage queen). If you don't find more than 2-3 mm, leave it alone. If you find more than 3 mm preload, start to worry. Check more often, consider clamping the shaft more securely. Check crank endplay more often. If endplay is approaching the 0.4mm spec limit, consider a prophylactic main/thrust bearing job.

Dannyfumi

Is the flexplate concern mainly on Autos??


Dan

Bill Ball

Yes, although there is some forward pressure on the thrust bearing with the clutch mechanism engaged in MT cars [EDIT: It's a REARward pressure, so the front surface of the thrust bearing wears in MT cars.]. Also, AT after 85 are the major concern as Porsche eliminated a shim-adjusted retainer that prevented the clamp from moving forward on the TT shaft.

tdelarm

Thanks Bill.

Unfortunately mine currently is a garage queen…more or less. But it’s still nice to know this.

bigs

I have asked Dave and Garrity at SLC Motorsports how often to check this issue. I drive my car roughly (I mean approximately!) 4K mi. a year. For that amount of driving, they just check the flexplate annually in the spring before the serious driving season begins.

IcemanG17

I drive about the same annual mileage as bigs......I figure one check per year is fine.....might as well do it at the same time as the oil change!

Bill Ball

Sounds reasonable. I drive 10-15k miles per year and check it about every 4 months and endplay once a year. Mine is a bit confusing as the preload has been as high as 5-6 mm in the past, and the shaft has APPEARED to move progressively forward. Most often now, it is 2-3 mm, so I could leave it, but because of the earlier apparent movement, I am a bit paranoid.

dr bob

Bill--

Is the shaft --really-- moving forward constantly, or is it taking up the same 3-5mms you are releasing each time? It would seem that an 'improved' flex plate and clamp, one with more flex and more clamp, would be the order of the day.

Many MB cars use a three-legged flex plate that has a big rubber spider at the front end, taking some more of the axial displacement and also a little of the torsional shock. If push comes to shove, an adaptation of that part might be a good permanent solution. At least for the street-driven non-supercharged cars.

Bill Ball

dr. bob:

Unfortunately I have no photo record, but each time I released the clamp for at least several times, it appeared to move progressively down the shaft, leaving less and less exposed flutes. I only had a smidgen of the flutes exposed now, whereas my recollection is there was a good 1/2 inch originally. I can't account for it. Also, I can't be positive this is the case. This is over almost 100k miles now since I bought the car for a total of 170K miles. All seems good despite all original parts. There is some whine in the TC area but that has been stable for 3 years. I worry very little about it. I just checked that everything is tight fore and aft, monitor the preload and endplay periodically and drive like I stole it.

ebs

Has anyone seen thrust bearing failure on an '84 (or older) car?

Ben

My car was manufactured in 84 for delivery Jan 85. My thrust bearing is most definately dead!