I am hearing a grinding knuckles noise and i feel it on the shifter if i rest my hand on it. It only happens when there is a load on the axle and i am excellerating over a bum or uneven piece of gorund. i replaced the tranny mount, but that only quited it down a bit. I guess there are spacers on the u-joint. is the motor twisting so much that the driveshaft is hitting my underbody? How do i fix this. My car is an original malibu but an SS clone, 454 big block 400 trans.

Look under the car, if it's hitting you should see the marks. If you think that you have a bad u-joint, remove the shaft and make sure the joints move freely. These are easy things to check before going deeper. Also, what do you mean by u-joint spacer?

My buddy was under there and the driveshaft was not coming out for some reason, and he got his dremel and was shaving off bolts or something. I am not sure what he meant by spacers either. But the engine flexing and some kind of stub bolt hittting the underbody makes sense. The grinding knuckles noise would be because of the speed of revolutions. But i will check under there tomorrow and look for scrapes. thanks