Wild Bill

Hello,
A friend of mine has a cherry 968 with 56K original miles that has developed a moderately high pitched whirring, scraping sound from the rear that increases in frequency and volume as the forward speed increases. It becomes audible at anything above 20 mph and it makes little difference when the clutch is disengaged. The brakes also impart no change in the sound being generated.

My first guess was a torque tube bearing going away, but shouldn't that change when the clutch pedal is depressed? A supposedly reputable local shop says he needs a transmission rebuild and quoted him a price of $9,000.00 to do the job! Yikes!

He is not having any problems running through the gears or with clutch engagement/pickup. Operates just fine other than the increasing noise at speed. What are some other possible causes he should be looking into... carrier bearings, CV joints, rear wheel bearings or ???

TIA,
Bill

luckett

It might be the infamous pinion bearing problem.

JimV8

I was just reading about sounds coming from the transmission on the 968 technical forums. Thats a good place for 968 owners to visit as well.

ATL944

CV joints would create more of a popping sound rather than a scraping sound.
I also have the same sort of scraping noise, it sounds like metal scraping against the pavement as I accelerate. Its sounds like its coming from the rear wheels. Couldn't have anything to do with the CV joints, because I had those replaced within the past year...

Wild Bill

Thanks for the input guys... I'll do some searches to see what I can find on the subject.

If it is the "infamous" pinion bearing, what would be a reasonable price to do the work? The $9k estimate has my buddy contemplating letting the car go.

Regards,
Bill

luckett

Since you can buy a used tranny for less than $3K, I would say $9K is a bit steep to pay for the repair. I'm not saying $9K is expensive for what the shop wants to so, which hasn't been detailed in your post. Just that you can get it repaired for less.

Wild Bill

Chris,
Going the used transmission route is what I initially suggested to him, IF indeed his tranny requires substantial work. I'm not yet convinced... but he's not mechanically savvy and simply told me the shop had told him he needed a transmission "rebuild" for this lofty sum.

I told him to get a second opinion and to change out the gear oil, while I researched costs and options for him online.

- Bill

saxman

I have a receipt from the PO of my 968 for a fix of the pinion bearing... somewhere in the $2500 range IIRC.

944-LT1

This might sound silly, but would it be possible to take out the CV's, rent a car dolly, and tow him around the block to see if it was the tranny and not a bad inner/outer bearing or hub/brake issue? That way the engine, torque tube, tranny, and CV's are no longer suspect?

If the noise is not there anymore, hook up the CV's but loosen the drivehaft to transmission input shaft coupler and slide it back and repeat to rule out the torque tube and engine? Effectively isolating the problem to the tranny and CV's.

Just sounds like a cheaper way to diagnose than spending 3-9K with the risk of it still being there when its all paid for and done.


It just seems really young for tranny bearing problems to me. But who knows.

saxman

the pinion bearing issues seems to have popped up in lower mileage situations actually...

went on my car at 27k miles

Luis de Prat

Indeed, it sounds like the ill reputed ring and pinion issue in the 968 transmission. For some reason, Porsche never assumed responsibility for this design defect that has affected many examples of this particular model.

I suggest contacting 944/968 transmission expert Kevin Gross (944 FAQ) for some ideas.

944-LT1

Did not know that. Thanks. Im assuming thats only with the 968 series transaxles and not others?
Is it a lack of lubrication? Or just bad preload from the factory.

EDIT: I see what you mean!!... bottom of page... http://ohv.pca.org/mart_main.html

944-LT1

http://members.rennlist.com/martin/faqs.htm

saxman

it was some issue with the tolerances on the pinion bearing during installation. Something to do with the automation of the process to my knowledge. Popped up on about 10% of the cars. Was replaced under warranty on my car.

I believe it was only an issue on the 968 tranny, but I'm just regurgitating information I've been told on the issue.

stolarzj

You should be able to get one rebuilt for around 3k, maybe not locally, but there are a few places that are familiar with them that they can be shipped to.