To the OP:
Is your truck 2wd? 4wd? 2 speed transfer case with 3.73 rear?
And what mode are you driving in when this occurs?
Try this test. Find a nice long steady uphill in a residential area where you can drive relatively slowly without traffic.
Put the tranny in “M”anual so you can feel what your drivetrain is doing without the transmission shifting on you.
Get up to 30 mph or so, and around 1800 rpm—whatever gear that may be. Just steadily cruise up the hill at a constant speed, in one gear, and listen— and feel for any surging or jerking.
Do the exact same test with it in 2wd, and in 4wd, and see if this is occurring in only one mode.
Obviously try to find a smooth well paved road for best results. The goal is a smooth steady pull, while putting a light load on your drivetrain (hence the long uphill).
Let us know what your results are