Thread: Wheel bearing hum??

Heat is a good pointer to trouble as you have stated, but have you checked your diff? When you apply the brakes, the diff is going into coast mode so diff noise changes also.

Jack up the wheel and give it a spin. Compare the suspect wheel to the others. Then inspect the bearings for wear.
Aaron

Jack up the suspect wheel and turn by hand (If a rear wheel chock a front wheel, as you will need the handbrake off. Should be absolutely smooth, no roughness etc. Also, depending on the vehicle type, remove the drive flange (and axle at the rear) and see if the bearings show any signs of contamination, especially if grease lubricated.

In this sort of technical question, it always helps to specify the model you are talking about.

And yes, applying the brakes lightly could damp out wheel bearing noise.

John

Thanks for your input guys. The vehicle is a 1986 County, so has the Salisbury rear diff.
Grokents reply brings up something I forgot to mention. I'd apply the brakes gently with my left foot while continuing to hold the accelerator so maybe this rules out [Quote]"the diff is going into coast mode"???
I recently had the rear wheel bearings out and they seemed to look OK, although it was a rush job done in poor light the night before I needed the truck, so not totally sure.
They were grease fed before this time but I removed the seal so they are oil fed now. Did grease them first though when reinstalling them. Also replaced the Diff oil since this time.
Will try jacking and spinning the wheels as suggested.
Thanks.

If it is a wheel bearing, can make more noise when you put more load on it, so at constant speed see if it makes more noise or goes quieter on a long left sweeping curve or a long right sweeping curve.