phil0618

Hi,

Did a bunch of research on here and elsewhere and looking for some validation
1994, 968 with LSD and 105k miles
Very well maintained

Car begins to make a whining/whirring sound as you approach 30+ miles per hour and at 40+ mph depending on the gear (and hence the rpm's of the motor) it can become the dominant sound in the car at speed s over 40.

The noise continues to rise with speed regardless of
Acceleration/deceleration
The clutch being depressed or engaged
The gear selected

The noise is NOT present at rest when revving the engine.

I do not notice a change when turning corners

Research seems to indicate several possibilities
Pinion gear
Wheel bearing
CV joints
Torque Tube bearings
LSD?

None seem a slam dunk, but here is what seems to be a concensus

Pinion - the ultimate test seems to be to accelerate to 80 and listen to a jet engine-like whoosh while the car decelerates while the transmission is in gear
- I get the noise commencing at 30+ mph regardless of accel/decel, clutch depressed etc.

Wheel bearings - many have said that if this is the issue it should be noticeably different when you turn corners. My noise seems unchanged when I corner.

CV joints - Not certain what best characterizes this noise?

Torque Tube - several said that when the bearings were going it was a louder more aggressive sound - like rocks in a tin can. Mine is a smooth whirring / whining sound that seems to go up in pitch as speed picks up.

LSD - This is in the list only because someone suggested changing the fluid and some part of the LSD and this made a big improvement.

So, here are the inevitable questions.
What does the brain trust say is the likely fault?, and
How should I proceed to diagnose?

Thanks,
Phil

blackboy

My vote is the pinion, not positive without hearing it though.

badcoupe

running it on the lift and listening with a stethoscope will positively pinpoint the source.

JimV8

Apparently the pinion noise is obvious to those who have heard it. See if you can hook up locally with 968 owners and have community listen-in.

TheBlau

Mine has the same noise you describe. I, too, have a 220/LSD car. I'm interested to hear your diagnosis.

bombfactory

Before I bought my car, I drove one that had a very obvious jet engine roar coming from the rear. If it's the pinion gear, you really can't mistake the sound for anything else. My 220 LSD rear end makes a mechanical whirring noise that goes up in pitch as the speed of the car increases (it's not gear or RPM dependent). I'm hoping this is just the normal sound of a healthy 968 transmission!

docmirror

Judging by the sound, and the tests you've done it sounds like a bearing or a CV. Could be a pinion bearing, or a side gear bearing, or a wheel bearing but something that is continuous is usually a bearing. The common failure mode is a bearing with the grease cover breached by water or dirt.

phil0618

I want to thank everyone that is adding to the post.

With the holidays and other priorities it will be a few weeks before I can fully diagnose, but I promise to post with whatever I ultimately find out.

Thanks,
Phil

phil0618

Hi all,

I finally had the opportunity to have this checked out and it is coming from the transaxle and the expectation is that it is the pinion bearing.

We put the car up on jacks and ran the car up to speed in 3rd/4th and the noise was noticable.

Now the question is what to do...? Mine is a factory LSD model.

docmirror

It's repairable. The pinion bearing defect is somewhat well known. I don't have a trans guy to call but you should be able to call around and find a shop that can take the trans from you and return it with the bearing swapped and the lash set.

The good news I've heard is that when the bearing starts to make noise, it'll go a long way before failure.

autosea

I just bought my first 968 yesterday and I really like the car. i bought it sight unseen , flew to pick it and when I saw it comming around the corner to pick me up at the airport I was very happy. Got in the car and we took off and right away I was thinking I wonder if the owner even notices the loud jet sound comming from the back of the car. Im stillvery happy but first thing when I get home the gearbox or whatever will be comming out. Thanks for the information. Mine aslso has limited slip option and I picked it up in oakland. I am on my way home now to Seattle driving up the coast. Maybe we can get a group buy fixing gearbox

touareg

We should both make a visit to Kevin, I spoke with him late last year, he said make an appointment and he would test drive.

Hope to do it in the spring.

EDIT: Just realized the comment was from 3 years ago

4kix66

Try Kahler's in Dublin. I think they have a bunch of experience with this. You sure have riches of great shops where you are in Campbell and thereabouts but Kahler's has had a 968 tech on staff for years. For a pure genius who is not Porsche specific try Fab Systems in Castro Valley and speak directly to Rocco.
Also reach out to Trevor. He knows everybody. Holy **** I just noticed age of thread too. My reply was to OP. I wonder how he solved the problem. My info is local to him.