Hello, my '04 4wd has a pretty loud rear end howl, it is a LS but dont think it's an LS problem, no noises or chattering when turning. Howling is loudest at 50 to 60, but some noise at all speeds. I don't mind tearing into the rear myself, but not sure if I could tell what was wrong just by looking, i suppose bad bearing might be obvious, but not sure how to diagnose gear lash tolerances.
Oh it only has 107000 mi. and is an 8.8 rear I believe.
Thanks

 

The front pinion bearing is usually the first thing to go, as it receives the least lubrication. it will be obvious by looking at it. As they fail, the rollers become grey and dull, with a mild bead blasted appearance, and get worse from there on. Gear failure, in and of itself, is rare. More often it is induced by bearing failures which allow the gears to chatter or run mis-aligned. Disconnect the driveshaft and attempt to wiggle the pinion. Any movement other than rotational is a bad bearing. Also, after a highway drive of 25-30 miles, how hot does it get around the nose (pinion area) of the housing. If its notably too hot to touch, you probably have a dying bearing.

 

Good call on the pinion bearing, I crawled under the truck, sure enough lots of side play in pinion. Just have to decide to do it myself or call shop.