• Planetary failure
  • Planetary wear


Insufficient lube oil and/or excessive clearances.


This kit offers replacement parts for rebuilding damaged rear planet assemblies and gives rebuilders the option of replacing only the worn components.

4L60, 4L60-E, 4L65-E, 4L70-E

Pinion Gear
Part No. 77731-01

Rear Planetary

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Sonnax pinion gear 77731-01 is a direct replacement for worn or damaged OE pinion gears in rear planetaries in listed GM transmissions. Helical pinion gear crafted from case-hardened alloy steel for added durability.

  • 4L60, 4L60-E, 4L65-E, 4L70-E Pinion Gear 77731-01