I have a 2000 Allegro Bay MHZ, Ford chassis Triton V10.
I do not tow. Intermittently, when climbing hills, the transmission will not continue to downshift as the speed decreases. I either continue uphill @ 20 mph or stop and it will upshift as I go further uphill.
Obviously, when I took it to the Ford truck shop I could not repeat the problem.
Any thoughts?
Thx

 

take a video as the issue is occurring so you can show them the issue, at least it will give them a start and will validate the claims...

 

My first WAG is that you may have a problem with your throttle position sensor. I believe this is what the PCM uses to determine how much power you are asking for, and controls the transmission as such. Just a guess though, but this is where I would start.