I have a 98 Ram 1500 5.9. Shifts perfect when first take off, but after driven for awhile it will not shift out of 3rd unless let off accelerator. Transmission was rebuilt about 25000 miles ago...issues with transmission or could it be something else I should check/try?

Recent work (last 5000 miles):
Hughes plenum kit
TPS
Plugs and wires
Transmission flush
Coolant flush
Both O2 sensors
Both speed sensors

Not sure if related or adds any info, but do have a rmp surge when between 55 and 60 on flat road. Had something similar years ago on a Durango and told it was a dirty throttle cable - cleaned and better. Not sure how to clean...next on list to try looking up.

Any insight would be appreciated.

 

adjust the tv cable

 

+1. And make sure fluid is full (in Neutral and warmed up).