A while back my truck would take a few minutes going down the road until it shifted into overdrive, but today it did fine...UNTIL I was going up a hill and it down-shifted, but never shifted back into high gear or overdrive.
I was running over 3k rpm's to go 55mph.
After work, I headed home and it never found high gear until going down a hill and would periodically shift to a lower gear (irregardless of terrain or speed), then back into overdrive, etc...
1st, 2nd, and 3rd seem to be fine.

Any insight is sincerely appreciated!!!

PS: I'm new to the forum, but not Yota's