On cold start loud pop (one time) from under truck when backing up then driving it ok, possible u-joints? 2001 F250 4x4
Thank you for all the informationCheck the entire suspension: front bushings, tie rods, ball joints; and rear axle U-bolts, leaf spring bushings; and frame rivets, and engine/trans mounts, and exhaust system hangers & joints... The TSB in the captions of this photo album is about older trucks, but the techniques described apply to yours:
(phone app link)
A telltale sign is fine red rust powder leaking out of a joint that's barely moving, but wearing badly.