Pinion Seal Replacement
How are Differential Pinion Seal issues diagnosed?
Diagnostics are simple for the pinion shaft seal. When oil is noticed to leak from the seal or build up around the seal, it will likely be recommended for replacement. Also, if there is play in the pinion shaft or driveshaft, any oil seepage from the oil seal will continue once the symptom is corrected, so the seal must be replaced. This is due to uneven wear of the rubberized seal on the pinion shaft.
How are Differential Pinion Seals replaced?
This difficult task is more physically taxing than anything, but also requires knowledge of setting preload on the pinion shaft bearing. Preload is the measurement of force applied to a bearing, and is measured by the force required to turn the pinion shaft. In some cases, the original position of the pinion gear nut can be marked against the pinion shaft flange, but this is not the proper procedure for all vehicles. In a worst case scenario, the differential cover is removed, and the differential is drained of oil. Then, the driveshaft and pinion shaft nut are removed so the pinion shaft seal can be pried from the differential housing. The new seal is installed with a drift, and the flange and nut can be reinstalled, but not tightened. Now, the drive axles, of various types, can be removed from the differential so the reload measured does not include the force of rotating the axles. Setting the preload for the bearings requires torquing the pinion nut, checking the force to turn the pinion shaft, and repeating until the pinion shaft turns at the specified tension, according to the service manual for the particular vehicle. Once complete, the driveshaft, axles, rear differential cover, and fluid may be replaced. Note, this is not a complete how-to, and there are vital steps which vary for individual vehicles, following the service manual is extremely important.