Wsp964

A week ago I posted a thread concerning a clunk when I blipped the throttle.

Thanks to the help of fellow rennlisters I had a possible cause : worn motor and transmission mounts could.

Today I went to a very known Porsche mechanic here in the aera. The guy is a mechanic for an official Porsche dealer but works on Porsches in his backyard during his eve's. I saw his proud in his garage : early 70's 911, upgraded with a 3.8 engine no less than 330hp, 2 additional oil coolers, Turbo breaks, competition suspension, cage, etc . Only 1060kg. His car pulls faster than a 996 Turbo !

He toke my car for a ride and suspects a drive shaft problem by what he heard. He will check it out tommorow morning and keep me posted. On my turn I will keep you posted.

Anybody else had drive shafts probs ?

thanks

kkim

Is your car a C4?

Wsp964

Nope, C2 Tip, aprox 36k miles.

kkim

So, by drive shaft problems, he is saying the something is bad with the drive axles/cv joints?

Wsp964

Yes think so. He will keep me informed of what exactly is wrong.

I saw a post of asimilar problem on the 964 forum. Bad drive shaft too. Replacement of a part of it made the clunk dissapear. Think the posts tiitle was "clunk between seats".

Monique

Humm... drive shafts are an unlikely cause. These are solid with no moveable part.

The CV joints are much more likely to cause some problems.

Good luck.

CalvinC4S

75% of the time a customer would bring a car in for a clunk when they blipped the throttle, I would find a golf ball under the seat. Seriously, check under your seat for loose objects as they resonate through the car and sound like a drive train issue.

Usually the CV's would make a popping sound under slow turns. How dose the clutch feel? Some times when the DM flywheel comes apart it will do strange things under load.

Wsp964

Bill,

Last week I did check under the seat and as you said, found a toy of the kids, a cd box !

But clunk is still there. Maybe some loose bolts or something. No dm flywheel as its a tip.

Waiting for the mechanic to give a call...

Wsp964

Got the phonecall. Don't really know what to think if but thik it sounds expensive news.

OK here my explanation if my best english.

So it s not the motor or gearbox mounts. It s not the CV joints or drive shafts.

The sound is comming from near the tiptronic gearbox. The mechanic told me he can reproduce the sound by turning the wheels. He used a stethoscope to locate the noise. Behind the actual gearbox is a kinda "box" with gearwheels (?) (toothed wheels). In this box are also conical bearings.

The sound is comming from there. He will wheck out the partnumbers to give me an idea of the cost of parts and repair (sik!). Engine and gearbox need to come ou of course to begin with.
He calmed me down by saying it is not the actual gearbox.

My knowledge of engines, gearboxes, etc is close to zero. So I ve got really no clue about what he is talking. Maybe someone can help me out.

Sorry for the bad explanation but I do not know the technical words for the parts.
Maybe someone can translate it in real english.

To be followed. Damn it all sounds expensive.

993inNC

That applies to front wheel drive cars, and his is a C2 so he has no turning joints. Usually rear CV joints cause a "shudder" under exceleration. It is the bearings in the joint passing back and forth over the groves it has created in the race portion of the joint housing. Used to see it alot in the old Mercedes SL's and 944's. But they typically don't make a clunk noise that would be that audible. He probably does have a bad mount, and thats forcing something against something else under hard excel. May want to attempt almost a "brake stand" type situation to see if there is excessive flex with the motor, the noise may show up then. Strap the car down for safety like you would on a dyno....wouldn't want to hurt yourself or any one else.

Well you type faster than me. Have no idea what that could be, don't have and experience with "tips", good luck.

Wsp964

Did some looked via search function. Saw a reply of Steve Weiner on a same kind of "clunk".

He wrote about a " pinion bearing problem". So fellow rennlisters, do you think it is this what the problem is ?

Well sure sounds expensive to me, any estimates ? ... how am I gonna tell this to the lady again !

Dan V

differential?

Wsp964

Ive got no idea, going to collect my car this eve. I ll ask for more details and $$$.

Did some look up on "pinion bearing". Seems that it s a known problem for a 924/944/968.
But it does not concern a tiptronic so guess its not that.

Oh well got to wait till this eve.

Toga

Wsp 964, I hope it won't be too bad for your wallet!!!
May be you could drop the engine at home, and bring it to your specialist...this would save you a few hundred Euros (600?). On a C2 it should'nt be too hard to do

Wsp964

Well I am just (literally) back from the mechanic and got some bad news. There seems to
be play or a bad bearing in the tiptronic gearbox, situated in the back part
of the gearbox, near the inermediate plate. It is a very rare situation as these gearboxes are very
strong. He told me that they normally do not rebuild a gearbox but simply
replace it with a new one. Cost 9.000 euro without tax and labour !!

There is an alternative : a rebuild by ZF. ZF is the manufacturer of
Porsche tiptronic gearboxes. It would cost less but still quiet considerable. You have
to take the gearbox in, they take it apart, contact you to say what exactly
is wrong and what the price will be to rebuild, you agree or not.

He proposed me to continue with it and see how it ends up. Might get worse,
might stay the same.
This is a recap of te situation as it is now ;

- when I accelerate in a normal manner all is OK, let's say building up the rpm, all is OK

- when I abrupt accelerate I can hear a "clack"/"clunk" noise
- when I abrupt release the throttle , same noise
- when I am in 3thrd gear and braking for a red light for instance and the
gearbox automaticallly shifts down to 2nd gear I hear the same noise
- when I "blip" the throttle (fast on-off movement), same noise appears

I am in chock ! Don't really know what to do ... sell the car ?? I hardly believe I would ever consider this.