Driver side front wheel bearing failure

[Doctor J]

Last week I noticed an odd noise while driving on 40 mph; it sounded somehow similar to the exhaust roar.
I performed several tests and noted that:

• The noise was speed-related
• I noticed it under acceleration, cruise, float and coast (that ruled out the transaxle final drive)
• It did not change when I shifted to neutral and even switched an engine off (ruled out engine and A/T)
• There were neither unusual play nor abnormal hub temperature

The noise was not evident when I spinned the front wheels by hand (one wheel at the time in the air, A/T in neutral)
"Lane change" test did not change noise.
The only one test that worked was the running car in drive with one wheel in the air and another on the ground; this identified the problem:

http://youtu.be/UBaX_HEOqIE


After replacing the steering knuckle with one from wrecking yard,
I took the bad one apart and noticed a single "pit spot" on the outer bearing race, picture below



According to our machine shop expert, it happened due to material defect, not the bearing abuse

The hub cross-section ( I lost my drafting skills over the time)



shows why it is important to properly torque the axle nut to 137 lb X ft on Camry
tightening the nut too much or with an impact wrench can jam the balls due to split inner bearing race (Gap B).

[Doctor J]

I think I found a real reason beyond the bearing failure.
On the outer surface of the race right opposite of the damage, I noticed dark gray discoloration



Such discoloration was not due to the overheating but to the fretting (contact corrosion).For definition see
http://corrosion-doctors.org/Forms-f...g/fretting.htm

to prevent this from happening again the outer race on the outside must be lubricated with caliper slide grease (which has anti-fretting properties)
Also, another critical step while assembling the bearing is not to "overperss" the inner race (color green). Unfortunately the manual does not specify the distance how far this race must go on the hub (Gap A)

[Doctor J]

The following steps are to remind the mechanic how to press the bearing properly
(Prior to these steps the steering knuckle is stripped of old bearing and seals and backing plate is installed)

• Place the steering knuckle on the press with bearing bore facing up; use PVC pipe connector or equivalent to support the knuckle
• Press the outer race with the balls into the knuckle using the old outer race or a metal round of equal diameter minus 0.02 of an inch (preferred) until it bottoms
• Remove a steering knuckle from the press
• Place studded hub with studs facing down on the bock or metal round or old bearing outer race; leave the hub on the press
• Press the front (outside) half of inner race on the hub using 39 mm ID pipe or socket
• IMPORTANT: install the outside seal on the steering knuckle
• Lower the steering knuckle on the hub
• Press the inside half of inner race on the hub shaft using large socket or equivalent

(Note: I would recommend measuring a gap “A” at the very beginning before taking bearing apart and placing 1.4 inch OD washer with thickness equal to the gap “A” on the hub shaft to prevent a race from going too far)

• Remove a steering knuckle assembly from the press; install snap ring, inside seal and dust deflector

[blu_91_cam]

Thanks for the detailed write up! Now I need to go and check my bearings, the front driver side sounds like a family of squirrels live in their.