How does one tell if a wheel bearing is bad? I'm getting a hum that is independent of engine rpm. Weight transfer (braking) seems to make it louder. When I jack up the front, the driver's side has some play (sure sign of a bad bearing on a motorcycle, but I don't know cars/trucks!). Rear wheels seem to move in and out a hair, but not "rock" like the front driver's side.

Truck is a 99 2wd XLT regular cab with 5 speed.

 

When you have the truck jacked up and try to move the wheel if it only has play rocking it side to side you generally have bad tie rods. If it only has play when rocking it from top to bottom you generally have bad ball joints. If it has play in all directions you generally have bad wheel bearings. On the 2wd trucks its pretty simple to just remove the brake rotor and physically inspect the bearings as well.

 

Front wheel bearings generally get way louder or it goes away depending on what direction you turn at speed. Can be a hum, generally a growl.

 

Update: I decided to go ahead and change the bearings in the driver's side as it had a little free play to it when jacked up, but as soon as I got it apart it was obvious that the bearings were in good shape. I replaced them anyway as I had already bought the parts.

The next day I chased down a nearly new condition spare tire and started swapping it around. Yep, it was a bad tire causing the noise. Live and learn! New pair of front tires is on the way.

BTW, Amazon has a killer price ($70) for Goodyear all terrain wranglers!

 

$70 is standard to walmarts everyday price for those tires. (fyi they will get tons of punctures - ive had at least 20 of em over the years - good tires otherwise)

yea bad tires kinda make a lulling wavey noise as you drive and changing lanes generally make the pitch different. They can cause the vehicle to pull if on the front. They can cause a growl depending on the tread type and depth.

You did the right thing by swapping around a spare tire (or borrow a friends known good wheel) to see if you can isolate the problem.