In my 98 12v i was driving down the road real easy and when i put it in 5th gear and get to about 1400-1500 rpm's real easy my truck will start hopping real hard (kinda like letting out on a real grabby clutch). It did it once in 4th gear too. I replaced my clutch about a year ago i cant believe it would already be going out. Maybe a fuel pressure ploblem? I dont know what the problem could be if anyone has a clue please let me know.
Thanks,
Blake

 

it might be slipping

 

does it feel like the engine is chugging? or is it running smoothly while this is happening. Mine will chug and shake the hell out of the truck if i've got the T/C locked up in OD under 1500RPm.

 

No it is running fine the only time it chugs is when my foot hits the pedal from it jummpin so hard.

 

Carrier bearing? Out of balance or bent wheel, bad shock, bad tire?

 

Mine is hopping because the track bar or drag link is bad.