i drive a 1999 dodge 2500 4wd. i've owned it for a year now. i have what feels like a broken engine or trans mount symptom. i have repeatedly checked for bad mounts no luck. when leaving from a signal if the accelerator is pushed for a normal take off there is a thud . it can be felt in the seat of my pants. also when cruising around 70 or so, if i let off the acceleartor there seems to be a noticeable backlash feeling. the u joints checked ok. is this normal??

 

How did you test for a bad mount? try a stall test with brakes applied and with the hood open to watch the engine twist, also slip joints will give a "thunk/snap" if they have play. and excessive rear end back lash will cause a noise too.

 

check out myabe your u-joints and your tranny mounts as well would probably cause it. also a long shot check out your leaf springs were they mount on the axle. i've seen on other trucks them slipping as well as bushings.

 

As dj posted, loose U-bolts will give a wicked noise as the diff tries to rotate

 

thanks guys. i will check it out and let you kow what /if i find