[aventuragrun metallic]

A couple of months ago, I started hearing a high pitched whine coming (I think) from the rear of the car. Starting about 35MPH, I can hear it when I am on the freeway. When I push in the clutch and coast, I still hear it so it's probably not engine-related. Just changed tires and the sound is still there. Any thoughts? Bearings, trans, other?

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[flash]

does it sound like a 727 climbing up your butt?

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[Chris Vais]

Actually more like a pair of J-79s running in full afterburner. Sounds like a pinion bearing to me. I changed mine when it got to the point where I couldn't drive the car for more than an hour without getting really agitated. Kind of like the way you get when there is something off in a sound system that makes you want to run away!!! Or like way too much expresso in the morning.

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[SILVY968]

Let's hear it for the pinion bearing. Sorry.
Brian

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[968Oz]

From another site

Pinion Bearing Failures
Everything you wanted to know and were afraid to ask:
What is a pinion bearing: the 968 has a transaxsle i.e. the gearbox, final drive and differential all in one unit. The gearbox output shaft has at its end a pinion gear driving the crown wheel. This shaft has a big 'pinion' bearing on one end and a smaller one at the other end. A pre-load is applied by way of shims and a nut at the smaller end of the shaft.
Symptoms: Road speed related whine audible from 35-40 mph. Test on straight road with smooth surface for minimum tyre noise. Close roof and windows, accelerate to 80-85 mph, lift off, if you hear noise resembling a jet plane slowing down on a runway - you have a problem ! Alternatively you can secure the rear of the car on stands, run the car in top gear and listen to the noise from the gearbox. If you haven't got LSD you can stop one or the other wheel to eliminate possible wheel bearing and CV joint noise.
Cause: Too much pre-load on the pinion bearing at assembly. Getrag ( who made these transmissions for Porsche ) uses a computer controlled robot, which has not always been accurate.
Repair: This requires complete dismantling of the transmission. Porsche allows 15 hours, but everyone says it is not enough. One London, UK, dealer quoted 40 hours at £70 plus tax = £3290 = over $5000 just for labour. Parts are not too expensive, but it may be wise to replace all the bearings. Setting the correct free play - 'backlash' while at the same time achieving the correct pre-load requires an accurate measuring instrument, choice of shims, patience and experience.
Make sure your mechanic / shop have the necessary skills.
Prevention: Check for leaks, correct oil level. It may be a good idea to change the oil at 20,000 miles or maybe even more often.

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[stewhatch]

Oz - this is great info. Thanks.

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[rxter]

Loads of other posts on this subject, findable with the search function. Of note it appears that failure is 1) very low frequency, 2) unpredictable, 3) unavoidable - if your unit is going to fail it will fail, and 4) indiscriminate (happens to manual, tips, open dif and both types of LSD).

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[ds968]

Six years ago, parts and labor cost me $ 2,050. In retrospect, while certainly not good news this is not a terribly expensive problem ( as opposed to a timing belt failure.. [img]style_emoticons/<#EMO_DIR#>/dry.gif[/img] ) . Also, I recall some people posted that they have driven years, 25 k - 30k miles or more with a pinion whine so not sure if the "failure" causes anything more problematic than that jet engine noise.. [img]style_emoticons/<#EMO_DIR#>/huh.gif[/img]

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[kwikt]

Yep, I'm at 30,000 miles of whine since i purchased the car. Who knows before this. I will however be tackling this job over the summer or maybe just replace it with a used whinefree unit!!!!

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[flash]

a couple of corrections / clarifications

low frequency - i think he meant relatively uncommon, rather than a reference to pitch, because it is actually fairly high frequency

it does not happen in tips - it does happen in manuals both with and without lsd

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[Cloud9...68]

Hadn't heard about a pinion bearing problem in quite awhile; there used to be posts about them all the time (although moreso on the old 968.net), so I was hoping that it had pretty much run its course, afflicting all the cars it was going to hit. Sorry to hear you seem to have the problem. If you can, shop around to try to get the best price (from a competent mechanic, of course), as there seems to be a fairly wide range of quotes, from what I remember. Good luck.

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[aventuragrun metallic]

Thanks for the quick feed back. The sound itsn't horribly loud. I only noticed it when the stereo was off. Could it be a low fluid problem? If it turns out to be the pinion, do you think I could replace with a used LSD unit more cost effectively than a rebuild?

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[flash]

if you want to roll up here, i can have a listen

as for the used lsd thing, the pinion bearing isn't related to the lsd, but i do know somebody with a good used one they would sell - i'm actually going to his house tomorrow

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[aventuragrun metallic]

Thanks for the offer Flash. However, I'm probably not going to have very many opportunities to steal away to LA any time soon. I'll just have my mechanic down here take a listen next week.

Regarding the LSD, thought it might be a convenient reason to upgrade. Otherwise, not really ready to make the change right now.

Thanks again.

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[flash]

well, i'm actually a LOT closer than that, but no worries

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[Chris Vais]

"Six years ago, parts and labor cost me $ 2,050."

Mine reached an unbearable level of noise at about 96,000. The repair was $2500, but I also replaced the synchros, and bearings. As I recall, most of the pinions failed within the first 100,000 miles or so and I don't know of anyone who had it properly replaced having to do the job a second time.

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[SILVY968]

When I had the whine, I put it off for as long as I could. My PM warned me, as did many on this board of catastrophic failure if the bearing lets go. When I got enough saved up to rebuild the trans, the bearing was so worn that when removed from the transaxle it came apart!
Price 2.5 years ago was $1800 for the rebuild and $500 for the R&R labor.
Brian

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[flash]

it can be VERY bad if it lets go - you can pretty much kiss the whole box goodbye - not something i would risk

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[firefish]

Someone told me that if you didn't see a problem the first 75000 miles you probably never would. He was referring to assembly and material problems.

Normal wear and tear should logically result in a little less noise in the beginning of the tranny life and then gradually increasing.

I would do an oil change first. I have used a Redline product with a friction enhancer (to aid when shifting and not to be used in clutch type lsd's) with great success but others may feel differently. After the oil change I would monitor the noise to see if it intensifies but since it is not audible unless you turn your stereo off I'd say you're most likely ok and that the noise/sound is simply a new thing that you have discovered (I get that all the time).

Perhaps get one of those magnetic plugs for the tranny and plan for dual or triple oil changes to thoroughly check for chips. Oil change is rather easy albeit a bit messy and oil is cheap compared to a unnecessary tranny rebuild.

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[flash]

if only that were true - while certainly not the norm, i have heard of quite a few that happened later

one of those mysterious quirks that is the 968

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