Engine/Transmission (1998.5 - 2002) Is it trying to downshift again or is it slipping?

[wcoomes]

I just returned from a trip to WY & Mt Rushmore hauling my large truck camper and towing my boat. While cruising along at 60-62 with the cruise on, I would encounter a hill and my transmission would downshift up to about 2500 rpm but after awhile on the longer grades it would hiccup like it was trying to downshift again to maintain speed or is the transmission slipping and need serviced?