4L60E 2WD Extension Housing with Output Shaft Seal

This is the GM factory rear extension housing (tail housing) for two-wheel-drive 4L60E and 4L65E transmissions, GM part number 24241496, and it ships with the rear output shaft seal already installed. The bushing is pressed in at the factory, so instead of pulling the old housing apart to drive out a worn bushing and seal, you unbolt the housing and put a complete new one on.

This is the fix for a 4L60E that has chewed up its rear bushing. The usual sequence is a worn slip yoke that wallows the bushing out, then the seal loses its lip and starts dripping ATF down the back of the case. You will hear it as a grinding or whine from the tailshaft area at road speed, and see driveshaft vibration once the yoke has room to move. Replacing the yoke without replacing the housing just wears the new yoke, so do both. Installation is six bolts and a gasket, and the vehicle speed sensor bolts straight back into the boss on the housing.

One thing to know before it goes on the bench: the speed sensor retaining bolt hole in the casting comes untapped. Run a 6mm tap through it before you bolt the housing to the case - the aluminum is soft and it takes about a minute, but it is a lot easier on the bench than under the truck. Shops also use this housing for 4WD-to-2WD conversions on 4L60E and 4L65E cores, since a new OE tailshaft is easier to source than a clean used one.