I put in a new nine inch rear end in my car it is a 87 IROC , along with a new custom drive shaft . The car has a bad vibration now . It starts at 1700 rpm and does'nt end . I tried to turn the drive shaft 180 * did'nt help tires are balanced . The car only started to do it after the install of the rearend . the rear has a detroit locker in it dont know if that matters . Any help would be great thank you .

 

Just lifting off at high speed triggeres it. It was reduced by putting a couple of washers under the transmount to add some angle to the driveshaft. Having it too straight can be just as bad as having it at too much angle. Try some washers under the crossmember bolts or trans.. they effectively change the DS angle in opposite directions.

ps, mine has an aftermarket torque arm that does not bolt to the trans. And adding washers is very effective on changing DS angle. If you still have the factory TA, it wont change as much with this method.

 

Thanks for the info , I do have an adj torque arm it is set at -2* . I fixed the problem the u joint caps that set in the rear end yoke were the wrong size , ahair to small . So I called them and they gave the right part # for the right u joint , and now it is smooth as glass . I'm glad it was an easy fix .