In 1st and 2nd everything feels fine, but when you get up into the 40+mph and in 3rd or 4th at part throttle...the whole car shakes up and down, but if you punch it or give it more gas for it to drop down a gear it is okay. Any ideas?? Wanted to go to the track this weekend and can't think of what it could be. I just changed out the o2's a couple of thousand miles ago and the opti has about 10,000 miles on it...and I have an MSD 6al. Wasn't sure if it was spark. Thanks for the help!!!

John

 

maybe its a broke or loose tranny mount or drive shaft out of balance. My car shakes terrible above 65. I'm buying a aluminum driveshaft out of a 99 camaro. Hope it fixes the issue. Good luck. Troy.

 

The couple tranny mounts I have broke, I never really noticed any vibration . The tranny would just jump under hard acceleration. Im running 4:11's and i have the same problem. Lot of vibration at higher speeds. I am pretty sure i can eliminate a lot of this with an LS1 aluminum driveshaft. My buddy put one in his and it made a huge difference with vibration.