Just finished a rear gear set on a 2016 F150 with only 1400 KM's on it, for an apparent vibration. I didn't do any of the diagnosis, the tech that looked at it didn't do any rear diff diagnosis either. Someone in management called the gear set. They road tested after and said "It drives smooth, but I never really felt the vibration in the first place." Our shop foreman is leaning more towards the torque converter because it only happens when the trans is hot and torque is locked and changes with engine RPM....I got that info after I finished the gear set.