I recently purchased a 94 LS400 of a friend for $500 with a slipping transmission. I got a new one and installed it. It drives good and switches gears smooth and at the right time. But I noticed when I'm in reverse the car doesn't roll back by itself. I have to give it a good amount of gas when backing up and I feel little clunks once it starts going. Also at stops while in drive I notice a lot of vibration from the car. There's not much vibration when in park. I figured out the there's a certain position the driveshaft has to go back in the transmission but I don't know what position it needs to be In. If anyone can help that'd be great. Thank you.

 

Vibration when not moving has nothing to do with the drive shaft. Vibration in gear and not much in park? When in gear the system is loaded, and vibration could be some messed up engine mounts. When (in) park there is no torsional load on the engine mounts like picking up the left side of the engine.

 

I jacked the car up today and looked and i found out my diff bushings are shot. The whole diff goes up and down when i put it drive and back in reverse.