993 grinding noise while slowly accelerating
 

Hi,

my 993 (135k miles) emits grinding (metalic) noises when accelerating at low speeds (in the 1200 - 1800 rpm area).

If I accelerate carefully (very slow increase in rpm), the sound is not audible.

Everything beyond 2000 rpm is just fine.

Car shifts gears nicely, is fast (went for approx. 80 miles @ 150+ mph without any strange noise) and does the nordschleife just fine, sounds great doing it ;). 21 mpg fuel consumption and a 1/2l of oil (10W40 btw) on the last 3000 miles.

Just the grinding noise does not grow on me... Ignore it and hope for the best?

Thanx for your time,
Dirk

I'd be careful going those speeds (150+ :eek:) while your car is making grinding noises from the drive train! Just because you don't hear it at high speed doesn't mean the grinding/noise isn't there. There's a lot of noise at those speeds to cover it up.

It could be CV joint(s) ready to let go. I wouldn't want a CV joint to fail on me at 150! Have you tried jacking up the car and turning the wheels by hand to see if you can narrow down the location of the sound? That is where I would start. CV's tend to make noise under load when they're bad (in my experience).

might also make sure IF you have a dual mass flywheel that its not failing.... they can get pretty noisy at low RPM. I saw a pictures of a failed dualmass flywheel and it damaged the bellhousing pretty bad.

I have a RS flywheel in mine and my gears rattle at low rpm, by 2k rpm everything is nice and quite.

The sound definitely disappears. If i leave the 1200-1800 rpm band there is no grinding at all.

No, i guess i have to check with a new mechanic. The last one said that this sounds normal for a car with this mileage. I drove a similar 993 with 100k miles and this lacked the noise though ...

Regards,
Dirk

Are you carrying a fire extinguisher?

A broken CV joint at speed could create some sparks!

I'm not saying that's definitely what it is, but that would be my first guess. I don't think any car should make a noise like that, no matter what the mileage is. I'd say it's time for a second opinion, or a new mechanic. Either way let us know what it ends up being.

Check this thread for results of a broken CV joint at speed: http://forums.pelicanparts.com/porsche-911-technical-forum/238313-cv-joint-failure-carnage.html And he was only doing 65mph.

I didn't think about the dual mass flywheel on the 993s. I know those can be noisy. My S4 has one too, and I dread the day I have to replace that thing.

The broken CV joint looks scary. I'll try to record the sound, maybe this sheds some light on the issue. And i speed up the 2nd mechanic review.

Thanx,
Dirk

Hi,

the opinion from my 1st mechanic stays the same: this is normal for 993 with the longer gear transmission ratio, some cars got it more, some less.

Slow acceleration in 2nd and 3rd gear from 1000 rpms to ca. 16000 rpm:

http://2scale.net/~dvl/accelerate-2nd-3rd-low-rev.mp3

The recording is not very good, but its possible to hear the grindy noise in the background (i assume gearbox). Other than that the car drives great considering the mileage (130k), but especially stop and go annoys me.

I'll visit another garage next week, but im interested in your opinion.

Thanx,
Dirk

can't get the link to work...

Doyle

Hm?

dvl@weird:~$ curl -O http://2scale.net/~dvl/accelerate-2nd-3rd-low-rev.mp3
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 728k 100 728k 0 0 594k 0 0:00:01 0:00:01 --:--:-- 626k

Works for me. Maybe your browser doesn't know how to handle mp3 files? Right-click and download as .....

Cheers,
Dirk