I have a 99 w/ 4.6L and a 97 rearend, replace prior to me buying the darn thing, anyhoo have a whirling noise when i am "coasting" (without giving it gas) mech said i need new rearend, but hes been wrong before. Could it be axle bearings or sumpin that would be cheaper than $600 for a used rearend???????

 

Unfortunately, drivetrain noise can be really hard to diagnose for somebody without a lot of experience. Even most mechanics don't have much, if any, experience with differentials. I'd say that the chances of you needing a whole new rearend are slim. It's most likely a worn bearing or the preload on the pinion bearings has opened up. Either way, it's going to have to be looked at by a drivetrain specialist to get a proper diagnosis. Find a local 4x4 shop, as they will have the most experience with your rearend. If you don't have one near you call around to some transmission shops.

If your rearend needs to be rebuilt, which it probably does/should, it will cost a pretty good amount. My local 4x4 shop charges $250/axle, which is by far the cheapest I've found on here or elsewhere. I'd say you'd be looking at around $350-$500 labor, +parts.