Today driving home from work on the highway my 97 4wd jimmy started to do something that ive never experienced with it yet. What i describe it is as if you are towing something and you take off from a dead stop and the get that tugging feeling from the rear. Problem is im not towing anything and im at highway speeds. The truck jerks and almost sputters but its not an engine issue, at least it does not seem like it. It almost seems like its coming from the rear end. Its not constant either it will do it randomly and only for a sudden jerky or tugging. What could be causing this. I know my rear wheel bearings were making noise the last couple weeks could these be causing anything like this?

 

The possibly failing bearings could be affecting the 4L60E trans & kicking it out of OD. That could happen when the diff gets warm & fluid is thinner.
Could be a parking brake issue.. but that's a grasp.
Check out Craigslist etc for a diff - just in case.
Just my opinion

 

How hard was it jerking? Were you running the ac? It could just be the compressor kicking on and putting extra strain on the motor.