Brought my truck in to a repair shop to find out the reason I hear a fairly loud whirring noise while driving. I was told I needed a new "rear end" as the rear bearing is worn out. What is the best approach here... if the bearing is worn, why not just replace the bearing? Don't know much about cars, and I don't want to get ripped off! THX!

 

A couple of quick thoughts. First is get a second opinion. There are numoerous bearings back there. You didn't say whether it was actually in the rear diff or perhaps the rear axle bearing which is farther away.

 

X2 second opinion

 

Got a stethoscope? If not, go spend $10 on one.

Jack the rear axle up on stands, run the truck in 2H and 2nd or 3rd gear. carefully crawl underneath and use the stethoscope to listen to the rear axle housing at both ends and the middle. Watch out for spinning tires which can hurt you real bad... don't run yourself over with your own truck.

This inspection will tell you which wheel bearing is noisy, or if it's your differential bearings. Otherwise, it could be a tire noise.

If it's a wheel bearing, check your axle flanges for run-out. If you have runout on the side that's noisy, you need a new axle and bearing.

HTH.