My truck recently devolped a bad whine in the rear end. It gets louder with an increase in speed. I put it up on jack stands and ran it in drive and the whine is there and increses with speed. Put it in rev. and there is no whine. What do guys think gears or bearings? 44000 miles, 9.75 rear end.

Thanks

 

I have the same problem with my 01. 9.75 rear end also. I'm bout to get into it and see if I can find anything wrong with it. Any info on this would be great.

 

There have been 9.75" whining threads the whole time I've been here. Some claim certain housings were manufactured to poor specifications and that the noise can never be fixed. Others have reported a variety of parts that were replaced by Ford, including ring/pinion, bearings, and entire assemblies. My 2000 9.75" began to whine at 1,000 miles. First, Ford said it was normal. Dealer 2 tried the typical "throw some parts in it" approach to no avail. I saw the rear cover off every time and noticed the factory pattern was off due to improper pinion depth. I got sick of the idiots and even though I was under warranty, I replaced the ring and pinion with U.S. Gear 4.10s and properly setup the pattern, paying special attention to pinion depth. It was perfectly quiet from then on. Here is how to properly setup or diagnose a pattern.

www.ring-pinion.com/tech/yukoninst.pdf

 

Thanks for the info and the link. Im leaning more towards it being a rining and pinion problem being that it doesnt make the noise in both directions.

 

You're Welcome ! Here's what the pro has on noise:

Scroll down to "General Information" and "Diagnosing Noise"

www.ring-pinion.com/tech/techind.html