ASE Automobile and Light Truck Certification Manual Transmission (A3) Practice Test

When a leaking pinion seal is identified in a crush sleeve type differential, it is essential to replace both the seal and the crush sleeve to ensure proper functioning of the differential.

The pinion seal prevents gear oil from leaking out of the housing where the driveshaft connects to the pinion gear. If this seal is leaking, replacing it is necessary to maintain the correct lubrication of the gears and to prevent further damage from low oil levels.

In addition to replacing the seal, the crush sleeve also needs to be replaced. The crush sleeve's purpose is to establish the correct preload on the pinion bearings. When the pinion seal is removed and replaced, the original crush sleeve may lose its ability to maintain the needed preload due to having been compressed during the initial installation. A new crush sleeve helps ensure that the pinion bearings are correctly preloaded, which is critical for the longevity and performance of the differential.

Thus, both actions are necessary: to replace the pinion seal to stop the leakage and to install a new crush sleeve to maintain proper pinion bearing preload.