Front Bearing noise...give some input?

[astrochimp]

So I've had both front bearing assemblies replaced in the last 3 or 4 years. Probably only 20k on them or so. I did the drivers side bearing with part from advance auto.
There is a loud humming from the front and obviously a bearing. It's Loud turning left and goes away turning right so I believe this verifies that it's the wheel bearing and NOT the front diff bearing.

Is there a way to 100% verify the source? the wheel doesn't seem to have any play in it when I try to shake it.
Can i change JUST the bearing and not the entire assembly?

I'd rather not put an entire assembly on Again and find out it wasn't the wheel bearing.

THANKSSSS

 

[koda2000]

4WD? 2WD? I assume 4WD. Wheel bearings tend to growl when they go bad. Not so much hum. I'm thinking for front diff bearings.

 

[astrochimp]

4WD but a diff bearing would not come and go depending on if you're turning left or right, correct?
since it's not getting any different load either way

 

[imp]

4WD but a diff bearing would not come and go depending on if you're turning left or right, correct?
since it's not getting any different load either way

Yer right there! I had a wheel bearing going bad, barely noticeable for several thousand miles, then got worse quickly. Before it reached that point, I put the vehicle on stands, all tires clear of the ground, high enough to slide underneath with my stethoscope. (it was a long plastic-handled screwdriver). Had my wife run it up carefully in Drive, 4X4 HIGH, to about 30 mph indicated. Using the screwdriver plastic rounded end to push my earlobe shut, the blade touching the center section (it was the rear), I easily ruled out pinion bearing noise, went to the area of the wheel hubs, sure enough, noise originated in wheel bearing, left side. Ordered complete new hubs with bearings on Ebay, they came complete with wheel lugs already pressed in, all I had to do was press the bearings into the knuckles. I did both sides.

I just HAD to see what the hell allowed that bearing to go a couple thousand miles without suddenly failing! It turned out to be spalling of an outer race, but not clear across the width of the race. IOW, the rollers still "rolled" over the bad place, but only out on their edges. The stethoscope method could save lots of headaches, but it's not without risk. Spinning parts can be dangerous. A tire rotating several inches off the pavement can grasp and hurl a dropped part with considerable force. Here's the bearing race: imp

EDIT: Another word of caution. If vehicle equipped with "4X4 AUTO", running on stands invariably has some unequal brake drag wheel to wheel, and the AUTO setting will throw the front wheels in and out of being driven, very noisily and repeatedly. 4X4 HIGH locks front in and prevents that. If "2WD" available, the rears can be checked that way. Fronts in 4X4 HIGH.

 

[koda2000]

Worn spider gears can cause a noise when loaded/turning one way or the other, but I guess you can't rule out a hub assembly.

 

[imp]

Worn spider gears can cause a noise when loaded/turning one way or the other, but I guess you can't rule out a hub assembly.

@koda2000 True enough! And, bad spiders would be kinda difficult to diagnose with a stethoscope. Could be done with a non-locker with one wheel on the ground. Come to think of it, if the noise were audible without steth., with the drivetrain running, car on stands, a bad hub bearing could be isolated by the wheel not turning. Getting a bit riskier, though. imp