Any thing is possible I guess, however I asked the mechanics twice over if they are 100% sure and they are.

The noise has been building for about a year.

The first time I heard it was right after a quick acceleration over a steep angled bridge and hard breaking as I crested over it. I must have upset something with the negative load. Unsure if that was the cause, but that's when the noise started.

Since then it has been progressively getting worse. The original problem with it was, that the noise would appear after some time driving and completely disappear when the car was cold - which made diagnosing really hard. I had an inkling - due to the above behavior that this may be linked to the diff or something that contains fluids - them being heated up and showing the symptoms.

It has gotten worse since then. By worse its just the noise which is more prolific and one can hear it even if the car is cold - so makes it much more easy to diagnose.
The car is completely drivable, handles fine - it's just the noise for now that a symptom.

I'm going to pull the trigger on a used front diff. Found one for around 1000 US. Scary stuff - it really is like playing Russian roulette. And there's only a 14 day guarantee. It's better than C$8500 with a two year warranty (OEM), any day of the week though

I'm also purchasing the seals separately (new) and I'll require the drivers side axle (will get a new one too). Those parts aren't too expensive, and if anything goes wrong once installed it makes diagnosis of the failure a lot easier if all the parts aren't "used".

 

I think i had told someone La Dismantlers before I know about that dif and its under 25k i believe. If they pulled for a customer that returned it. make sure its for a turbo.

 

The first symptom of a problem in my 996 C4S was a very subtle gear whine that could be heard at highway speed. That whine lasted for a couple of years and it continued even after changing the front differential fluid. The next symptom was a leak from the front end, originally just a few spots on the garage floor. Shortly after the leak, I began to hear a noise from the front end on deceleration. It sounded like a belt slipping. Once the leak and the sounds began, it deteriorated rapidly.

 

I found one for $800 with free shipping from LA Global Parts. It's the correct part number (997 349 020 50). Now it's wait and see.

They do have a 14 day guaranty (from date of delivery).
Not much but I should know very quickly if the part has any issues.

 

Be careful the turbo has some sensors that regular ones dont

 

Shouldn't be an issue.
That's the turbo part number, triple checked (Mechanic verified).

 

On my 996TT I took the front diff out and never looked back. I'm able to run whatever tire sizes I want. Steering is more responsive and connected. Never really worried about traction when running wide wheels and tires. I LOVE IT.

Obviously that's a 996 and the 997tt AWD is a much improved system. But since it needs to be replaced anyway, why not take the front diff out, run it for a while and see what you think?

 

Hey HIX, that crossed my mind until I read VID's thread (link to it one page back).
...Also I live in a wet part of the world, and with the added power I'm about to throw into it, I'd find myself wrapped around a tree faster than a hippy on ecstasy!

 

i feel for you , when i first bought my 2008 , used. I noticed an intermittent metallic knock. I run stock wheels and tires. I suspect it was like this when i bought it, my fault for buying it sight unseen. I'd like to think that the prior owner did not notice it. And just chalk it up to dumb luck. The knock was pretty scary sounding, like the frame was tweaked or something.
Took it to dealer , who ran it through a series of diagnostics . And couldn't diagnose the problem. Took it to local independant who specializes in porsche, who diagnosed the problem right away. Yup- front differential. I looked up part numbers , and bought one with correct number, off of ebay, and had it shipped directly to the shop. Of course , my mechanic verified that it was the right one before i bought it. When it arrived, it looked way different than the one that came out. And would not fit. I guess he found out that there are different parts for different cars? The part from ebay was $1300. He had to return it and bought a used one that fit , for $2400. $2400 labor for everything . $4800 total - runs perfect. Love my car and the sure traction of the awd. Although i never drive it anymore.

 

That sounds exactly like what I am experiencing, even down to my mechanic verifying the part. Hmmmm - now I'm a little more worried regarding the proper replacement part.
Is it possible to have the same part number for two different parts?

 

if i remember correctly, i believe it had a different part number. And there was no way of knowing what had been originally fitted to car without removing it? It was really strange. You're welcomed to call my shop. If they need to call me to release my service records , i will gladly let them . Reid vann in st louis mo.

 

would 245/325 tire combination screw up the diff?

 

Was there something wrong with your drivers side axle? Is that related to the differential failure?

 

Thanks - I'll reach out if need be.

Yes, they said that the drivers side axle needs replacement together with the two seals, and of course the front diff.

I haven't had a chance to inquire exactly what went wrong or how it failed as yet - I'm waiting for exact info on where it failed.

I'm starting to think that this all may be chalked up to an improper front strut plate installation (about two years ago). The puzzle pieces are starting to align.
At that time I had taken the car from Vancouver, down to San Fran (coast drive), up through the interior (Yosemite) and back to Vancouver. 1/3 of the way through I was getting serious clanging noise from the drivers side, over bumps. Turns out that the OEM strut plate was installed incorrectly and the top of the strut (the threaded part) was hitting/rubbing the edge of the fender "hole" that it penetrates. The shop later owned up to installing it correctly and corrected it, but wondering if this led to the problems I'm having now.

Since then I have replaced the OEM parts with Tarett plates.

 

Those are confirmed proper sizes - not an issue:
F Size: 245/30/20
R Size: 325/25/20