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

Arominus

The CV's are more of a Clicking noise (usually), I'd look into the lash between the pinion and big gear (I'm retarded and can't think of its name). It's probably loosened up a bit over time. This requires removal of the transaxle and likely professional help for the actual adjustment.

My 924s had terrible whine, and I always felt this was why. The transaxle had 200k+ on it and though it looked to have been apart I figured the pinion and such were worn and out of spec creating the noise. It was worse on decel. My 944S has a little bit of the noise but not anywhere near as bad.

968 GUY

968's are well known for pinion gear whine. Not sure if there is a set speed it begins the noise. Wheel bearings could be part of the problem but I would suspect the pinion. Not sure of a transaxle repair sho, but look around.
Good Luck.

Van

Tires? What brand and what age?

I don't know about 968 gear boxes, but I start with front wheel bearings (easy) and hopefully not get to rear wheel bearings.

Jfrahm

Can you replicate it with the car supported on jackstands? Support the rear A arms also to avoid running with the axles maxed out. In this configuration you might be able to localize the sound.

car_slave

Whining noises can be very tricky to diagnose. Is there someone who you could swap tires with? I'd try everything before getting the gearbox rebuilt.

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

FRporscheman

If you want to try a different set of wheels/tires, I have a set you can try.

Do you hear the noise more from the front or the back?

One way a friend and I narrowed down pinion bearing noise on his car was to remove the trunk carpet and go for a drive - the tranny is right below the trunk's floor, and without that carpet, the pinion noise got much louder.

Usually rear wheel bearing noise is like a thump or womp, and at 65mph it's fast so it may sound like a muffled drumroll.

No way it's torque tube bearings, if it only depends on vehicle speed and not on engine speed. I.e., if you coast at 60mph in neutral and hold the clutch down, the driveshaft will stop spinning - you still hear the sound, right? It's something connected to the wheels (bearings, axles, ring&pinion, etc).

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.

FRporscheman

The most common choices are to find a used 6-speed transmission (likely without LSD), or have yours rebuilt. Call Carlsen Porsche and ask for a quote, and make sure you're sitting down.