Transaxle Differential Side Bearings
Side bearings are tapered bearings pressed onto the differential case. They allow the differential case to spin inside the transaxle case. Side bearing preload adjustment is essential to the differential's operation. Manufacturers use shims or threaded adjusting nuts behind the bearings race to adjust the preload. Proper preload keeps the case from wobbling inside the carrier and adjusts backlash between the ring and pinion gear.
If this adjustment is too loose, the differential case will move in the transaxle case, resulting in damage to internal components like the ring and pinion gear. If adjusted too tightly, the bearings will overheat, resulting in premature wear.
Differential side bearings are rotating in all gears. When faulty, they make a whining or rumbling sound traveling forward that increases with vehicle speed. Use a torque wrench and a special adapter to check the side gear preload.