The sun shell for the 4L60 and 700R4 holds the reaction sun gear in second and fourth gear. The hub around the splines of the shell tends to fatigue after time and break. Every 4l60e and 700r4 build should have a new one. We sell a few options. “The Beast” is an improved sun shell made for race applications. It works in any model and comes with a thrust washer.
We also sell a hardened sun shell that is more durable than the original, and half the price of “The Beast.” For regular builds, this sun shell is our preferred unit. This hardened sun shell has two variations: the washer style (it has four square slots for the washer’s tabs), and the bearing style (typically 2001-up).