A complete master overhaul for the GM TH400 / 3L80 Turbo 400: friction clutches, hardened steels, molded pistons, gaskets, and the full seal and O-ring set in one box.
When a TH400 is coming completely apart, whether it is a worn truck unit that slips and leaks or a street and strip build behind a big block, the Coan 22107 master overhaul kit puts every friction, steel, piston and seal in one box. It is built for the 1965-and-up Turbo 400 family, including the 3L80 name GM used on later trucks, and it is a common kit for builders who want a known clutch count from a racing transmission specialist instead of a generic parts-store kit.
Bands, bushings and a filter are not part of this kit. Shipping weight is about 15 lb.
The TH400 is a three-speed hydraulic unit: the forward clutch applies in every forward gear, the intermediate clutch holds second, and the direct clutch applies in third and Reverse, with the front and rear bands and the roller clutch completing the hold devices. Each clutch is applied by a piston sealed with rubber lip seals. With age and heat those seals harden and the bonded factory pistons can leak, so even fresh frictions slip because the apply pressure bleeds off. The 22107 addresses both sides at once: new molded pistons with new seals to hold apply pressure, and new frictions and steels to carry the torque. A plain overhaul kit only stops leaks, while this kit replaces the parts that actually wear.
Pull the pan and read the debris. Friction material says clutches, brass says bushings, steel says hard parts. A pressure test tells you whether the pump can still make line pressure; a worn pump or pressure regulator bore will kill a fresh set of clutches. Our TH400 common problems and fixes guide covers the usual failure patterns, and the TH400 pump failure guide gives the pressure numbers to compare against.
The kit is listed for the GM TH400, Turbo 400 and 3L80 automatic, 1965 and up. Clutch counts in the TH400 vary by application and by build: heavy-duty trucks and modified drums may run more plates than this kit's count. Count the plates in each drum at teardown, and if you are adding plates for a high-horsepower build, confirm the drum and piston combination first. If you are not sure what your unit has, send us the year, vehicle and VIN or ID plate code. Everything else for the unit is on the TH400 parts page.
If the pump is scored, pair the kit with a rebuilt TH400 pump, and a TH400 shift kit shortens shift overlap so the new clutches last. The TH400 rebuild wear points guide lists the hard parts and upgrades worth checking on a performance build.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It covers frictions, steels, molded pistons, gaskets, seals, sealing rings and O-rings. Inspect the bands and bushings and buy a new filter separately.
It is catalogued as 5 forward, 5 direct and 3 intermediate frictions. Count the plates in your drums at teardown; a modified or heavy-duty drum may need a different kit.
Yes. The 3L80 is the name GM gave the TH400 from 1987, and the kit is listed for 1965-and-up TH400 / 3L80 units.
Factory pistons use bonded seals that harden and crack with heat and age. Molded replacement pistons give the clutch a fresh sealing surface so apply pressure holds and the new frictions do not slip.
A current licensed DEXRON ATF. Prime the pump, add fluid in stages since an empty converter holds several quarts, and set the final level on the dipstick at operating temperature.
