I have a 1986 pickup 720 that has started vibrating, rumbling, and shuttering when the transmission is engaged. When coasting in neutral this doesn't happen. While accelerating it rumbles and vibrates and almost feels like the engine is choking out, however im pretty sure its not the engine as this only happens when its in gear. The rumbling is accompanied by very frequent intervals of what feels like a biting friction from i think the tranny. It was an on off sort of thing but now it always does it. It is the worst in the mid range of rpms with it tappering off at higher rpms and is the worst in 5th gear and decreases in severity as you go down the gears. anyone got any ideas??

thanks

Welcome! Look at your mounts.

I looked at the mount on bottom of transmission and the mount itself looked alright but the bar i was sitting on was bent. Could this be the problem?

You might want to trace it and find out how/why it is bent. If your motor/tranny mounts are not holding things strait, then this could cause your problem.

word.thanks for the help man!