my truck has just started making a new sound...not good sounding either. when i have it at a certain rpm it sounds almost like something in the rearend is spinning wrong. but thats if i turn my head to the back of the cab. its not so much speed as it is rpm's though. mainly in the 15-40mph speeds. it sounds like it could be valves, or possibly something in the tranny? it did slip today which was odd at 40mph never done it before, i was slowly speeding up thought i usualy speed up faster than what i was going.

i remember reading somewhere you can hear the lift pump going bad, correct me if im wrong, it is the original pump too 235k miles on it.

if you need anymore info i will try to provide it.

TIA david

 

Try posting in the 1st gen area.