I have a vibration problem from about 40 to 80 or so maybe higher in speed.I have put on a poly tranny mount and the tranny has been built. Could the drive shaft be out of wack. I have read some of the posts and it says to try the 180 method. Can some one explain this to me in detail so i can try. It used to have 2.73 gears now has 3.42. It is an auto with 4k stall. I have changed out the wheel bearings. What to look for on drive shaft to see if it is bad. Can the lca be bad. if so what to check for on the lca. I am going to switch back to the rubber tranny mount and see if that helps any. What can i do to see what the vibration is...You can put your hand on the inside of the car where the driveshaft runs and feel the vibration inside the car. From where the arm rest all the way back to the back seats end. help me..

 

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I went through that with my 01 WS6 but its a M6, after I had the tranny built I installed an LS7 clutch kit and while I had the tranny out I put on LT's, 3" ORY and after my first track run with the new stuff I noticed a little vibration but it was around 2800-3200rpm no matter what gear or speed I was traveling. I did the 180 driveshaft fix and it didnt change anything, also I had recently took my torsen limited slip unit out to repair a bolt that backed out and busted off on the housing for the 3rd time so I was like you and wondering if I didnt remember to mark my driveshaft the last time I removed it since theres about 4 different lines i've marked from the removals. Last time I had a bolt break on the Limited S Diff I ended up researching more and it seemed my pinion was riding up the ring gear bad and causing all my problems, so I rebuilt ring and pinion and while bolting the T/A to the tranny tail housing I noticed my OEM tranny mount was split in half and I had never heard any tranny noise. I installed a E/S poly mount and everything was solid as a rock, I went so long I guess with the OEM mount and rear end slopiness that I didnt notice anything, but after the poly mount I did notice a vibration almost like my clutch or driveshaft was wobbling when I would come down in rpm and it got in the 2800-3200 range. I found a lot of people saying to grind the 2 humps down on the poly part of the mount to decrease vibration and not to use the washers/spacers and after doing that I havnt had any issues and its been 4k miles. I dont know if u have an E/S mount, or if the auto's have the bumps on the mount like with the M6's, but you could give it a try or check into it if so....