Ive got a friend with an 02 (no cad) that has a persistent low roar at 50-60mph. It sounds like it is in the left front and can be felt, slightly, in the floor. First thought is wheel bearing but it quits completely with the front driveshaft removed. A competent local mechanic has completely disassembled the shaft and it appears perfect. Any thoughts?

 

could be the U-joint right by the front tire.

 

One of the ways I like to locate sounds is get a stethiscope with a rod on the end , a comin tool from the tool trucks and good parts house's and touch areas with truck running on lift.