May have run the diff a little low in fluid and have developed a not so smooth rear end whine. The ring gear looks unmarked. Would it be a bearing gone out? Any suggetions in how to diagnose? Can it be detected by jacking it up and listening?

 

Here's an expert's opinions on rear end noise. Scroll down to "General Information-Diagnosing Noise Part 1 & 2"
www.ring-pinion.com/tech/techind.html

 

Some rear ends have a problem with it, my 2003 had it form the get go, the only fix is a new rear axle assembly. My 2004 has it and they are replacing the rear end, it only has 544 miles on it, go figure.

Brian

 

Had it torn down and gone through today. Replaced all the bearings, pinion bearnig was bad, all else was fine. Do not use Valvalene sp? Syntech lube. It cost me this $500 repair by foaming slowly out the breather while doing a 2-day open track at Fontana earlier this year. I don't normally think of checking the diff fluid level on such a frequent interval. What a P.O.S lube. (I was runing Ford friction modifier).

Good info on the above link, thanks.