4L60E / 4L65E 2002-Up Hardened Reaction Sun Shell (A74624B)

The reaction sun shell is the part that kills more 4L60E and 4L65E units than anything else in the case. The factory shell is thin where the splines tie the sun gear to the shell, and under towing, tuning, or high mileage those splines crack and strip. When the shell fails you lose reverse first, then the forward gears follow, and the unit drops a load of steel into the pan. This is the 2002-up hardened replacement, part number A74624B, built for the later 34-element style used in 2002 and newer trucks and cars.

It is the correct casting for the 2002-up 4L60E and 4L65E, and it replaces GM part numbers 24229604, 24217145, and 24229825. The steel is hardened through the spline area that normally lets go, so a shell you install during a rebuild is not the piece that brings the unit back apart six months later. Rebuilders swap this in on every teardown for these late units because putting a used factory shell back in is how you end up doing the job twice.

Fitment covers 2002-2014 GM applications running the 4L60E and 4L65E, including 2001-2013 Silverado and Sierra, Suburban, Avalanche, 2002-2006 Escalade, and 2001-2003 and 2005 Corvette. Verify your shell style before ordering: this is the later 34-spline 2002-up piece, not the early 1982-2001 washer-type shell. On the bench it drops onto the sun gear and indexes into the input carrier exactly like the original.

What is in the box: one hardened reaction sun shell. Reuse your existing sun gear and thrust washers unless they are worn.