The rear planetary assembly in GM 4L65-E and 4L70-E transmissions frequently wears out and must be replaced. Planetary assembly wear is generally caused by insufficient lube oil and/or excessive clearances. Lack of lube causes excessive heat in the pinion gear area and causes the roller bearings to gall the gear bores and pinion pins. If there is excessive thrust washer wear or endplay, the roller bearings can run without fully contacting the gear bore, causing premature failure of the assembly.
Sonnax planetary rebuild kit 77732-RK contains the replacement parts necessary for rebuilding damaged five-pinion planets.