The amount of force exerted on wheel bearings is astounding. Each bearing is required to smoothly control the rotation of the wheel to the tune of about a thousand revolutions per mile, support the transfer of power to the wheels for rapid starts and sudden stops, and handle the powerful lateral twisting force of the tires changing direction against the pavement — all while supporting a vertical load of hundreds of pounds. And, we expect them to perform flawlessly just about forever? Not realistic.
The “Achilles Heel” of a wheel bearing is the seal. Although wheel bearings can fail due to damage, improper installation or material imperfection, the most common cause of failure is the seal losing its ability to hold the lubricating grease in and/or dirt and water out.
However, the best seal, applied to the best wheel bearing, cannot be expected to last if not correctly installed. This primer can help you properly service Subaru wheel bearings.
Front stub axle seal replacements require special precautions. The seals are pressed into a side bearing retainer, which must be removed to replace a leaking seal. The side bearing retainers also control front differential side bearing preload, as well as ring and pinion backlash.
When replacing a stub axle seal, mark the position of the side bearing retainer before un-threading the retainer. Remove only one side bearing retainer at a time, or you’ll risk disturbing the differential adjustments. If you’ve marked the position before removal, the correctly installed position of the side bearing retainer will be obvious, as you will be unable to turn the retainer another complete turn.
The driveaxles on some Subaru vehicles are pressed into the wheel hub with a light press fit. Blasting the axle out of the hub with an air chisel, center punch or other implement of destruction invites damage to the wheel bearings. All of the force brought to bear by these methods finds its way to the wheel bearings, possibly damaging their races or balls. Special tools are available for removing and installing press-fit driveaxles. Ignoring these cautions invites a comeback for noisy wheel bearings shortly after your CV axle repair work.