Drive line noise mystery? Solved

[snailexpress]

(03-16-2018 )alborz Wrote:  Thank you for your advice
What’s the purpose of tortion bars? Do they keep the axles in place from going side to side?

yes the torsion bars keep axle in place from side to side. Grinding noise mostly from u-joints not in proper angle. Could be axle off set or frame height not set to specs.
Cheap shops have no idea how to set suspension they just putting parts how they think is OK.
Some words about laser 3 axle alignment system. Mechanic take measure distance from drive axle to most rear, then from most rear to the middle axle. Left and right should be the same. If front axle not perpendicular to the frame stupid computer user will set rear axles wrong. They trained to do so by Hunter Laser system manufacturer. Computer will print 00-00-00. Everything is good
Differential case angle is important too. If rear springs set not right it will eat u-joints and destroy differential input shaft bearing.
Try to find your truck suspension specs from dealer and check.