Vibrating / Abnormal Noise

[Flying V]

Hi Guys,

Last weekend I took my 996 GT3-MK1 to the track. After a few warm up laps, I noticed each time I would go thru fast corners, there would be a abnormal sound on the rear of the car. The sound sounded like as if the wheel was rubbing against the fenders. Besides the sound there would be a vibrating sensation. However when I checked the car by lifting it, there are no signs of wheel rubbing. The sound is consistent whether the car takes left or right corners. When I take the corners slow, the sound doesn't appear...it's only when there is "g force" in rear portion of the car during turns when the sound and vibration would appear. One guess that I have could be the engine support....

Thanks for your inputs in advance guys!

Godspeed!

[ltcjmramos]

Several years ago, I had a similar sounding problem driving my 993TT. Much to my embarrassment, it was loose lugnuts. I'd been doing track events for many years, and for some reason, this time, had failed to check the torque of the nuts after a session. Ended my day early since I couldn't find a problem, drove all the way home, no problem (luckily). Drove it to the dealer. Tech took it out with me, heard the noise, tightened the nuts.

Edited November 29, 2008 by ltcjmramos

[clord]

Hi V..... It's hard to determine what you are experiencing, not being able to hear the sound ourselves. It could still be wheel rub... do you have stock size tires/wheels in the rear? How about suspension parts.....all stock?

[Flying V]

Thanks guys for the inputs. Will check the lugnuts. The car is completely stock and original...this being the case I am open to the possibility that the shocks needs replacement if the noise I coming from wheel rubbing.

Godspeed!

[Chuck Price]

Do you hear a droning sound? That is what a worn bearing sounds like, and it would be heard when the rear is laterally loaded.

[topmech0]

my guess is the noise you refer to is the differential in the gearbox! some of the gt3 do this. but obviously check kug nuts and play in wheel bearings too first!

[clord]

Hi V.... Since your wheels and tire sizes are stock, it is unlikely that you are hearing tire rub. Worn dampers would not necessarily allow the tires to rub. As mentioned above, it could be wheel bearings, but GT3's are not known for wearing their rear bearings prematurely.....and, it's unlikely that both would wear out evenly such that you hear the sound equally on right and left turns. A noisy LSD differential could create the same sound on right and left turns. Mk I and Mk II LSD diffs do make noticeable noise on very slow speed turns, both going forward and backward(they are clutch type, asymmetric, 40/60 lock up)....., I've not heard mine at speed, though. And, if worn, I would expect the LSD to make less noise, not more. Certainly, loose wheel bolts can make noise and need immediate attention. If that's the problem, before you just torque them up, check the bolts and wheel holes for wear. I've seen loose steel bolts/studs hog out the bolt holes in alloy wheels. Please let us know what you find.

[Flying V]

Hey guys! Just want to give an update on what's wrong with my car. Apparently it's the transmission support that needs replacement. The rubber on the support has worn out, so when the tranny is subjected to g force during turns, some part of the tranny and the mounts would be metal to metal. I'm so glad that the extent of the problem wasn't so bad. If it was the LSD, it would have cost me some $$$$$$$$$$$$$!

Godspeed!

[clord]

Very interesting, V. Glad it wasn't big $$. Thanks for the feedback.