El Dario Loco

Hi!
I've had a slight "clonking" noice coming from underneath my car since a couple of years. It's noticeable at very low speed, mostly when I lift off the gas pedal a Little too fast. Haven't really noticed any problem with the handling but I don't track. The issue got Little bit more pronounced when I changed to semi-solid trans-mounts. The car is a 07 manual 997 TT with 110k km (70k miles), no tune. I have never noticed any leaks underneath the car and they have never mentioned anything after service.


Asked my tech to check that and they say that it comes from the front diff. They disconnected the front cardan and the noice almost went away. I'm told that the front diff needs to be changed but not a big hurry yet. The say that there also seem to be an "abnormal play" in the gearbox and that this needs to be adressed too.


Have anyone had similar issues? I can't really find anything when i search the forums. Any advice?
- Can the diff be repaired? A new one costs around $8k!
- Any aftermarket diffs out there that are better than original?
- What can be wrong with the gearbox??


Did not need this right now
/Darius

lliejk

I was reading in prep for receiving my 911 and found a post on 6Speed (went looking quickly and did not see it this AM, but I will look later) about a front differential issue.

The feeling was that too large a discrepancy between front and rear tire sizes caused the problem. His issue was the snow tires he chose to put on the car.

One poster asserted that these diff's can be rebuilt, even though the dealer says no.

When I find the post I will reply again with the link.

Ed

lliejk

Here is one:

https://www.6speedonline.com/forums/...replacing.html

and another:

https://www.6speedonline.com/forums/...y-one-had.html

and another on tire sizes:

https://www.6speedonline.com/forums/...5-s-rears.html

Neither of these was the one I read, but they should get you started, especially the first one.

Ed

El Dario Loco

Thanks alot Iliejk! Obviously you're better at searching forums than me. I'll have a look at the threads and see if I find any tips!

IMI A

If you remove the front drive shaft the clonking will go away but you will only be 2wd. This is what I will do when the inevitable happens. Re the gearbox just stick some transmission mounts on.

Try and find a good Indy as they should be able to tell you all this themselves if they have not already.

New the front diff is circa $5000 but you should get a used one for much less

JG 996T

This does come up from time to time. Also search/check 996 turbo forum and 6 speed. If mine were toast, I'd probably just get rid of front wheel drive system.

Skwerl

I thought the 997TT's AWD system wouldn't let you simply remove the front drive components? I know it's relatively easy on the 996TT but I thought it wasn't really possible on the 997TT because of PSM and all the electronics.

El Dario Loco

After checking some more forum threads including the ones Iliejk suggested there seem to be some concerns regarding RWD conversion of the 997 TT:
- Major suspension modifications are needed to make the car driveable, i.e. conversion to a GT2 suspension.
- Problems with the PSM and Sport mode that need to be solved by a ECU flash
- New LSD since some think that the turbo LSD will not be able to handle the increased strain

I'm not sure how much of this is true or just based on theoretical reasoning. The advantages would be (beside not having to spend >7k on a part that might fail again in the future) is significant weight reduction and improved steering feel.

I know another well-reputed indy that I can call for a second opinion. Maybe they have some experience with this issue. I feel that the best solution would be to refurbish the diff, maybe with some improved internal parts. To buy a used diff seems like a crapshoot.

El Dario Loco

I already have Torque Solution transmission mounts on. That actually seemed to make the CLONKING noise worse.

IMI A

You should not have any problems with a 997 turbo if you just remove the driveshaft and do not touch anything else. i.e. leave the front diff etc installed.

The people who have tried and failed are those who are basically trying to replicate the GT2 and remove the whole front diff etc. Removing the driveshaft as mentioned before should fix your clonking issue and also give you RWD.

On the transmission mounts if you go for track based semi sold mounts of course this will increase NVH!

gogoevo

For what it's worth this was my case.

https://rennlist.com/forums/997-turb...eleration.html

El Dario Loco

Ok, more sucky news. Now they tell me that there also is a slight "play" in the gearbox and that it'll probably need a rebuild/repair in the near future. The car has never ever been tuned or tracked! Getting close to giving up on this s**t right now

monty007

oh man - sorry to hear! What rims/tire combo are you running? Did you go for a second opinion yet?

El Dario Loco

The rims have always been original on the car with original size Michelin pilot sport. The only thing I know is that when I bought the car the rear tires were newer than the front but the tread depth was ok.

Just sent an e-mail to another renowned tech for a second opinion.

Macster

There has to be "play" in the gearbox. The gears are not interference fit parts.

My opinion is if the transmission/diff is not making any noises like howling groaning, shifts ok, stays in the gear you put it in, and is not manifesting any real signs of any problems, and is not showing any leaks, the transmissin is fine.

For the clonking noise this can be sometimes a self-inflicted problem. Every car's drivetrain has "play". The trick to avoiding hearing this play in the form of clonks is to be easy on and off the gas especially at low speeds in low gear.

Unless the front diff is manifesting more in the noise department than the clonking and it is leak free and especially if you change your driving technique to try to avoid using the car in such a way that produces the clonking noise I'd hazard an opinion the front diff is ok, too.

But obviously I have not been at the car have not heard the noise. So a second opinion as you indicated you are doing is I think a very good idea.