pc_mechanic

When I let up on the accelerator It seems like the driveline is vibrating as if it is out of balance. 99 3.8L w/automatic transmission.

RyansQuick6

Sounds like it may be ujoints

NeoTokyo

My U joints are starting to go bad and thud when I let off or when I am at a stop and let off the brake.

So +1 to Ryan.

I am just waiting to swap driveshafts to an aluminum one, I will replace them then.

mustangman02232

crawl under the car and see if you can wiggle the drive shaft, if there is play its u joints, there cheap and easy to do if you have the right tools, or it could be something as stupid as a weight falling off the drive shaft