Parts Master PM4278 Differential Pinion Seal

The Parts Master PM4278 is a replacement differential pinion seal designed to maintain the integrity of your vehicle's rear axle and drivetrain assembly. This seal prevents gear oil from leaking past the pinion shaft and keeps harmful contaminants out of the differential housing, helping to preserve bearing and gear life.

Manufactured from fluoro-elastomer (FKM) rubber, the PM4278 offers excellent resistance to high operating temperatures, gear oil, and the mechanical stresses associated with normal drivetrain operation. The precision-formed sealing lip maintains consistent contact with the pinion shaft to provide a reliable, long-lasting seal.

Key Features:

• Inside diameter: 1.812 in (46.02 mm)
• Outside diameter: 3.096 in (78.64 mm)
• Fluoro-elastomer construction for superior heat and fluid resistance
• Designed to meet or exceed OEM fit, form, and function specifications
• Helps prevent differential fluid leaks and contamination ingress
• Direct replacement for worn or damaged OEM pinion seals

Cross-references include National 4278, Timken 4278, ACDelco 4278, and other equivalent part numbers. The PM4278 is an essential drivetrain seal for maintaining proper differential fluid retention and protecting internal differential components.