i borrowed my buddy's 82 jimmy (automatic). I was driving, slowed down and then when i went to go accelerate the truck again, it wouldn't go anywhere. I turned the truck off and then started it again, same thing happened. the truck will run fine. i can put it into a gear it just wont engage( it will be in drive and i press the pedal and the engine revs). the tanny fluid is fine and the linkages are fine. i tried to put the truck back in park and it makes something like a grinding sound. the last time it happened i put it into 4 lo and then back into 2hi, then put it back in drive and it worked. the tcase was in 2 hi all the times this happened. Is his tranny dead or tranny or do you guys have any other suggestions?