Possible drivetrain whirling noise - most noticable bet 25-35MPH any t

[Porca911]

Hi all, I purchased a 2002 C4S tiptronic at the start of the year and I have noticed that there is a whirling type of noise when I drive it which is most noticible at around 25-30 MPH. Now you need to be tuned into it to realise it's there but now that I have I can't hear anything else.

I have changd the oil on the front and rear differentials to see if that made any difference as I read some threads about the front diff being not the strongest, but I don't think it has made any difference. The front diff's oil was clear which may suggest that it has recently been replaced, the rear differentials oil was rather dark so probably needed changing.

I think it is coming from the rear of the car, and you can also hear it if you engage neutrul as you drive along. Not sure if that rules out the tiptronic box - thoughts?

So I was wondering if there is any way that I can try to figure out where the noise is coming from. Obviously a wheel bearing would be the easiest or cheapest fix and probably my best case scenario. Would I be able to figure out if it is a wheel bearing if I jack up the car and spin the wheels and listen carfully? Do they fail or are they a common failure? I have never owned a car which has had a worn rear bearing in my years of driving so far.

But I have watched some vids online which say that the gearbox's also have sealed bearings like the IMS bearing which can fail/wear prematurely for the same reasons as the IMS bearing, so I guess it could be one of a number of things.

So have any of you experienced a similar issue and do you have any tips on where I could start or is this a specialist garage job?

Thanks,

Sam

Edited May 28, 2012 by Porca911

[Doohan]

the 996's are full of strange noise coming from every part of the car, the most of the case there are no problems, the only things you can do is check with Durametric or PIWIS for warning codes and doing the normal maintenance. But, if you can be mor specific with a single noise, maybe we can help!

[logray]

I don't think you are hearing the IMS bearing... that one doesn't whine.

The trans can start to whirring/whine when the internals wear.

The engine does sound a little like a sewing machine if it is bone stock...

If you have gearbox whine it's usually pretty distinguishable from an engine whine.

Can you get the car on a ramp or dyno and poke around to see where the noise is coming from?

[runeberggren@gmail.com]

Wheel bearing most probably. In my case the noise varied when doing left or right tuns. Or can can it be the whining noise from a defect AC?. Turn off the AC to test.

[rattles]

Check the alignment of your rear wheels and also check for wear on the inside of the rear tyres, I had a whine in my car at those speeds and that is what it turned out to be. Fixing the alignment wont stop the noise though if the rear tyres are already cupped.