transmission in the truck is a rebuilt one when driving at highway speed it will

You call that an answer. Silly Boy

Just call it like i see it! Like everyone else. Some just need glasses! Thick ones! . Possible lockup torque converter operation, have it scanned to see if lockup/unlock coincides with the shift!

when the truck down shifts it won,t shift back to the higher gear unless you stop for a while. If its the troque converter does that have to be replaced Thanks Terry

Any warranty on the reman?

no not now