TH350 Automatic Transmission Master Repair Kit SM-9

This is the complete soft-parts and friction package for rebuilding a GM Turbo-Hydramatic 350, the three-speed automatic that sat behind small-blocks in Chevrolet, GMC, Pontiac, Buick and Oldsmobile rear-drive cars and trucks from 1969 through 1986. It also covers the lock-up TH350C variant. ATP part number SM-9.

Inside the box: friction/clutch plates, steel plates, the pan gasket, all case and pump gaskets, rubber lip seals, metal-clad seals, sealing rings and the O-ring set specific to the TH350. The frictions and steels are the parts that actually wear out, so this is the kit you want when the unit is already on the bench and split open rather than a seal-only gasket kit. Components arrive vacuum packaged to boards inside sealed bags, which keeps the thin steels flat and the seals uncontaminated until you need them.

Typical bench order: strip the case, wash and inspect the drums and the direct/forward clutch housings, then set clutch pack clearance with the new frictions and steels before anything goes back together. Replace the pump seal and the rear extension housing seal while the unit is apart. Air-test each circuit at the pump face and the valve body land before the pan goes on. The TH350 will not tolerate reused frictions on a burned direct clutch, and glazed steels are the usual cause of a unit that shifts fine cold and slips in second once the fluid comes up to temperature.

Not included: hard parts, the front band, the filter, the torque converter or bushings. Order those separately if inspection shows they are worn. A stock TH350 build is roughly 3.5 quarts to fill the pan and about 10 quarts total with a dry converter and cooler lines.