Mysterious Grinding Noise when Turning in my '02 996

[vinceruth]

Hi everyone - First, let me say that these forums have been a fount of info for this novice and I appreciate the work that the volunteers do as well as it's members positive attitudes & suggestions. One of the few places with a true sense of community. And I see a lot of the internet in my job.

I'm driving a 2002 996 C2 Coupe 3.6L Tiptronic and I've recently developed an issue whenever I'm turning in either direction when accelerating in the turn - there seems to be a rubbing/grinding sound from the rear like driving over rough ground. Gets louder the harder I press it.

I've taken it to a reputable independent, Tre Motorsports and after I looked through the forums - suggested to them to look for bad wheel bearings, motor mounts, stones in the brake calipers, etc but to no avail and they are still kinda stumped. They drained the differential oil and found a few particles (I know that's not great) but not enough to outright deem it the cause/issue - they re-filled and said it could be the beginning of an issue with the transmission. I should also add there is a slight whine when I let off the accelerator and the mechanic noticed it when we test drove. Oh - And I did recently change one of the left rear tires as well.

So my first question is this: anyone else have an issue such as this?

Second - rebuilt tiptronic transmissions - I've gone to several sites and see that they are far more reasonably priced than getting direct from Porsche - any one more reputable than another and are rebuilds reliable? Anyone get one?

[beauar]

did they look at the wheel bearings? My Gf's Audi had to have two wheel bearings replaced and from what you are describing it sounds like the issue. I don't get it personally with these german cars having these bearings go bad. I would have them look at the bearing pack to see what the damage is. All I can think of.

If it is a wheel bearing it will get louder with speed obviously...since it is happening on turns I am a little stumped. Does it happen all the time or occasionaly? Does it happen when driving straight at lets say 30mph? if its on turns and from the rear I would suspect it might be something with the suspension rubbing on something as the suspension takes a load on a turn. Another thing to consider is that you can't just replace one tire in the rear unless they are of the same type and wear characteristics. Tiptronic transmissions have problems with this. This is at least what porsche told me but I have a manual trans and they said it was okay as long as it wasn't a tiptronic. Come to think of it.....this is probably your issue. Different tire traction and the trans is getting messed up. I would recommend replacing the other tire with same brand etc. Anyone else have any thoughts on tires on a tiptronic and issues with the trans.

Edited August 27, 2009 by beauar

[vinceruth]

did they look at the wheel bearings? My Gf's Audi had to have two wheel bearings replaced and from what you are describing it sounds like the issue. I don't get it personally with these german cars having these bearings go bad. I would have them look at the bearing pack to see what the damage is. All I can think of.

If it is a wheel bearing it will get louder with speed obviously...since it is happening on turns I am a little stumped. Does it happen all the time or occasionaly? Does it happen when driving straight at lets say 30mph? if its on turns and from the rear I would suspect it might be something with the suspension rubbing on something as the suspension takes a load on a turn. Another thing to consider is that you can't just replace one tire in the rear unless they are of the same type and wear characteristics. Tiptronic transmissions have problems with this. This is at least what porsche told me but I have a manual trans and they said it was okay as long as it wasn't a tiptronic. Come to think of it.....this is probably your issue. Different tire traction and the trans is getting messed up. I would recommend replacing the other tire with same brand etc. Anyone else have any thoughts on tires on a tiptronic and issues with the trans.

Yup - they said they looked at the bearings and it wasn't the case - and yes, it only happens when I'm turning hard, never on a straightaway. The tire I replaced is identical to the other one - had to hunt for it - and the good tire had very little wear on it, maybe 2500 miles on it, and local road driving, not hard driving. Good to know about the matched tires & tip issue, I never heard of it...

[roadsession]

I am having the exact same problem

So just recently my car has been experiencing a rough, grinding sort of feeling when I am accelerating around a turn or bend.

It happens at speeds as slow as 35mph and upwards.

Smooth as silk when going straight -

Smooth when coasting around a turn -

Rough when accelerating around a turn.

It may or may not be related but I did an autocross last week....and oh yes - my rear brake pads are getting thin but no brake pad warning light yet.

Any thoughts?

Thanks

Edited November 1, 2010 by roadsession

[roadsession]

Well went to the dealer this AM. It appears transmission mounts are shot

[roadsession]

So this is a copy of the repair order.

Note that the transmission mount and drive shaft are 997 parts now.

[PILFILR]

How many miles does your 996 have? What was the bill for this repair? I wonder if this problem is common. My 2003 996 TIP has 18k miles and I get a bit of a low grade hum from the trans when making a right turn at speed. It could be the early stage of this problem?

[roadsession]

How many miles does your 996 have? What was the bill for this repair? I wonder if this problem is common. My 2003 996 TIP has 18k miles and I get a bit of a low grade hum from the trans when making a right turn at speed. It could be the early stage of this problem?

Yes... I have 55K miles on the odometer.

The repair for JUST transmission mount is probably around $700 but I had a drive shaft problem too so total was $1700.

I don't think it's mileage, it's age. The car is 8 years old and I do track it...