U joints or hanger bearing would be my first place to look and push up and down at the diff to see if the pinion bearing is Ok.
The best way to check the ujoints is to drop the shaft so you know how it feels for each joint, not too loose, not too tight, no play.
After that make sure your hubs are disengaged, physically turn the front shaft and make sure each front axle turns freely.
I had 1 locking hub idler bearing go bad and " self engage" the hub while driving down the road, not good.