reggiegums Posted 18December, 2019 Report Share Posted 18December, 2019 My 993 develops a nasty vibration when the speed goes past say 110kph. The vibration seems to come through the rear and the gearbox. The steering is fine. Swapped out the wheels and the vibrations is still there. Running PSS10s and bushings seem good. Anyone have any suggestions? Quote Link to comment Share on other sites More sharing options...
Zelrik911 Posted 18December, 2019 Report Share Posted 18December, 2019 Driveshaft universal? Quote Link to comment Share on other sites More sharing options...
T-Man Posted 18December, 2019 Report Share Posted 18December, 2019 Look at the basics first.... Tyre condition Wheel balance Bent rim Then maybe driveshafts, wheel bearings/hubs, suspension... Quote Link to comment Share on other sites More sharing options...
LeeM Posted 18December, 2019 Report Share Posted 18December, 2019 I'd go wheel balance first. If you've hit a pothole, bump or even a raised 'non gender specific inspection hole' lid can throw off wheel weights JV911 1 Quote Link to comment Share on other sites More sharing options...
reggiegums Posted 18December, 2019 Author Report Share Posted 18December, 2019 Thanks fellas. I swapped out my wheels from my other 993, balanced and new tyres. very minor difference. The vibration seems to come from the rear. almost no vibrations through the steering wheel. Looking online, it may be the dual mass flywheel and maybe crankshaft also. Sounds expensive. Quote Link to comment Share on other sites More sharing options...
Stephen Tinker Posted 18December, 2019 Report Share Posted 18December, 2019 But if the vibration is road speed sensitive (110 km / hr) as you say, then engine speed is not the problem. If the vibration occurs @ a certain rpm in any gear, then the problem would probably within the engine / transmission itself. Quote Link to comment Share on other sites More sharing options...
Merv Posted 18December, 2019 Report Share Posted 18December, 2019 Transmission mounts tight and functional? Quote Link to comment Share on other sites More sharing options...
Rob Posted 18December, 2019 Report Share Posted 18December, 2019 Have you checked the tightness of the driveshaft bolts? They are renowned for loosening over time... Quote Link to comment Share on other sites More sharing options...
reggiegums Posted 19December, 2019 Author Report Share Posted 19December, 2019 2 hours ago, Stephen Tinker said: But if the vibration is road speed sensitive (110 km / hr) as you say, then engine speed is not the problem. If the vibration occurs @ a certain rpm in any gear, then the problem would probably within the engine / transmission itself. Very good point. Thanks you. 2 hours ago, Merv said: Transmission mounts tight and functional? Will check 2 hours ago, Rob said: Have you checked the tightness of the driveshaft bolts? They are renowned for loosening over time... Will check Forgot to mention that its a turbo thats been modified to run only RWD. I appreciate the suggestions very much. The mechanic is running the car on a rolling dyno today so will hopefully we can rule out several possibilities and narrow it down. Quote Link to comment Share on other sites More sharing options...
Stephen Tinker Posted 19December, 2019 Report Share Posted 19December, 2019 20 hours ago, reggiegums said: Forgot to mention that its a turbo thats been modified to run only RWD. I appreciate the suggestions very much. Well, that changes everything.... Quote Link to comment Share on other sites More sharing options...
Stew F Posted 20December, 2019 Report Share Posted 20December, 2019 Check your wheel bearings. Also, does it happen in different gears at the same speed? Quote Link to comment Share on other sites More sharing options...
Merv Posted 21December, 2019 Report Share Posted 21December, 2019 As I said check your engine and transmission mounts. Did they fit poly mounts and not rubber? The poly mounts really transit vibration. Ask me! Quote Link to comment Share on other sites More sharing options...
reggiegums Posted 26December, 2019 Author Report Share Posted 26December, 2019 Thanks for all the feedback. The mounts and suspension had all been done recently by the previous owner. Mechanic put the car on a rolling dyno and it was the drive-train. Turns out that when disconnecting the front wheel drive, the previous owner simply detached the front diff and axel and placed a cover. The drive shaft was spinning freely and wobbling around at higher speed. My mechanic simply disconnected the driveshaft from the rear and problem solved. case closed. Thank you all. LeeM 1 Quote Link to comment Share on other sites More sharing options...
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