• Planetary failure
  • Planetary wear


Insufficient lube oil and/or excessive clearances.


Sonnax 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 Pin
Part No. 77731-02K

Fits 4-pinion rear planetary.

Package Quantity: 4

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Sonnax pinion pin 77731-02K is a direct replacement for worn or damaged OE pinion pins in rear planetaries in listed GM transmissions. Hollow design features lube holes to reduce planetary burn-up.

Pinion endplay factory specification of between .008" to .024".

  • 4L60, 4L60-E, 4L65-E, 4L70-E Pinion Pin 77731-02K