Anyone know what this could be? When climbing hill/mountain roads my truck seems to "shift" up and down constantly until I crest the hill or give it more gas to actually shift. I use the quotes around shift the first time because the rpms don't move during the "shifting". It feels like I'm feathering the gas pedal. I believe it to be the Torque converter locking and unlocking. Why would it do this?
2006 4x4 auto sr5, 120k miles, no cel codes.