TCI 228600 TH400 Racing Overhaul Seal and Gasket Kit

TCI part number 228600 is a soft-parts overhaul kit for the GM Turbo Hydra-Matic 400 (TH400, also called the 3L80) built from 1966 through 1991. It carries the wear parts that get replaced every time the case is torn down: the front pump seal, the rear extension seal, the internal lip seals, the metal and Teflon sealing rings, the pan gasket and the valve body gaskets.

This is a wear-parts kit only. It does not include friction clutches, steel plates, bands, bushings or a filter, so plan to order those separately if your teardown shows burnt frictions, a glazed band or scored bushings. It is the right kit when the hard parts and clutch packs measure good and you are resealing a unit that leaks, loses line pressure to cut sealing rings, or slips on engagement after sitting.

On the bench, pull the pump and use the old sealing rings as a size reference before cutting them off. Soak new lip seals in ATF, install rings on the pump stator and output shaft with assembly lube so they stay seated when you slide the drums back on, and check that each drum turns freely before the next goes in. Use the new valve body gaskets in the correct order against the separator plate and torque the pan and valve body bolts to spec.