Wheel bearing?

Recently I have started to hear a droning sound coming from somewhere on my '03 4Runner(113K). Last time I heard a sound like this it was a wheel bearing on my '00 Camry that needed to be replaced. The sound is in addition to the normal sound of the tires, and is most noticeable when I’m rolling along at 30-50 mph - sort of like the sound of a DC-3 only not quite as loud. I am concerned that when I take it in I’ll be met with a shrug or a “you’re too sensitive!” What is the proper diagnostic sequence for figuring out the source of the sound? Can bearings be inspected for wear? Could it be the differential?

If the wheel bearing is enough worn, the tire/wheel will have play in it when it is on a lift and you grab it top-to-botton and find there is play in the wheel. If not that bad, while still on the lift, spin the wheel and see if it makes a slight “growl”. This means the bearing is shot but not enough to make it have “play”.

The next time you’re driving listen to see if the sound disappears or changes when you turn one way or the other. If it does the bad bearing is likely on the side toward which you are turning (i.e. turn left, sound lessens/goes away, the bad bearing is likely driver’s side).

Actually, I thought I noticed a change in the sound going around a curve today!

Jack up the front wheels off the ground in neutral with the back wheel chocked. Spin the front wheels by hand. You should be able to hear noise or feel vibration from a bad wheel bearing.

“Actually, I thought I noticed a change in the sound going around a curve today!”

Exactly. cigroller’s right. Find a relatively deserted interstate or a nice long back road. Take a few people with you. Don’t tell them what you’re up to. Cruising along at a steady speed, with the sound happening, ask each person where they think the sound is coming from–front or rear.

If 4 out of 5, or 5 of 5 say front, for example, that’s more indication it’s up front. Now SAFELY do a little swerve left, staying in the lane, though. Do it several times. If the noise disappears momentarily, then it’s probably the left front wheel bearing. (or if everyone thought the noise was coming from the rear, then you would go with left rear).

You see, when you swerve left, the body rolls right, taking weight off the noisy left wheel bearing, and causing the noise to disappear momentarily. Take your time getting the gist of this test–it’s just common sense. BE SAFE. And remember, if the sound doesn’t disappear when you swerve, it could be 2 bad bearings,–I hope not.

I don’t know if you work on cars much, but with, say, one axle off the ground, engine off, in neutral, and four wheel drive in neutral if possible, or out of 4 wheel drive, e-brake on (or wheels chocked) slowly rotate a tire. At the same time grab the coil spring, if it

has coil springs, for that wheel and feel for a slight vibration in the coil spring. Do both sides. For example, if the LF coil spring gives no vibration, and the RF does, it’s probably a worn RF wheel bearing. Please post back!