Differential Whine
 

Hello All,

My '96 F150 shortbed, 2WD, 302, A/T truck has 108k miles on it. Runs great but has slowly developed a whining sound that appears to be coming from the rear end. Its pitch increases and decreases with speed. It is not related to the transmission as I have put it in neutral while rolling and the sound does not change. Its also not related to engine RPM. I checked the diff fluid and its full and clean, although the diff was uncomfortably warm to the touch after a 30 minute drive home in 90 degree weather. The ends of the axle tube were cool, so I believe the axle bearings are ok. I've only owned the truck for 3 months, so I don't know the history. I really appreciate any thoughts. Thanks!

Welcome to the board and I am sure one of the guys will have some advice for you soon.

First, ruled out tires?

There are three main bearings inside the differential - two axle/carrier bearings and one pinion.

Could also be a gear problem. If you're going straight with same size rear tires, that may tend to rule out the spider gears, leaving ring and pinion.

Bearing noises tend to vary in pitch with speed across all speeds. Gear noises tend to get louder in certain speed ranges.

Had problems with a Jeep and a Massey-Ferguson where the ring gear had loosened.

Differentials will get quite warm when driving - not sure how warm 'uncomfortably' is. Just a WAG, but I would think 130degF is not unusual. If it's in the 150+ range, that would be a concern to investigate.

Thanks WDE3477,

You can hold your palm to the case without pain. I'm going to relax about it and see if the noise gets louder. In fact, with the a/c and radio on as normal, its hard to hear. I really appreciate your thoughts. Glad to be in the forum and I look forward to helping other Ford owners. Thanks again.

i had a similar problem after owning the truck for 10 months. while doing a burnout i found what it was. Rear u-joint. But it also popped. it ended up snaping the part of ear off the yoke and drive shaft...