4L60E Reaction Sun Gear Shell - GM Genuine 24229604

The reaction sun shell ties the reaction sun gear to the reverse input drum in a GM 4L60E. It carries torque in every forward gear and in reverse, and on a worn or abused unit the splined hub in the center of the shell is where it gives up. Once those splines strip or the hub cracks away from the shell, the transmission loses drive and reverse together and the pan fills with steel.

This is GM part number 24229604, the genuine OE reaction sun gear shell supplied through ACDelco and built to the GM factory specification. GM lists it for the 4L60E, 4L65E and 4L70E. It is the correct replacement when you want the factory part back in the case rather than an aftermarket heavy-duty design.

On the bench, pull the reaction carrier and sun gear, then lift the old shell off and check the center spline and the drive tangs where they engage the reverse input drum. Any rounded spline, cracking at the hub, or wear at the tangs means the shell goes. Inspect the sun gear splines and the thrust washer or bearing that rides against the shell at the same time, since a failed shell usually leaves damage on the parts around it. Confirm your transmission model and GM parts catalog fitment for your vehicle before ordering.