TH400 Overhaul Kit 1965-1996, new and ready to install. Fits the TH400. Ships fast from the USA.
When a Turbo 400 is slipping, burning fluid and leaking, and it is going back into a truck that tows or a car making more power than stock, a basic gasket set is not enough. This is a new high-performance master rebuild kit for the GM TH400, also sold as the 3L80, covering 1965 through 1996. Despite the overhaul-kit name on the listing, it is a complete master kit: an upgraded Raybestos performance friction module, a full steel module, the overhaul gasket and seal set, high-energy bands, new bushings and a filter. It is aimed at street performance, towing and higher-torque builds.
The TH400 holds its three gears with three multiple-disc clutches (forward, direct and intermediate), a front and rear band and two one-way clutches. A seal-only overhaul kit restores sealing in each clutch and servo circuit, but it leaves the frictions, steels and bands that actually transmit torque. This kit replaces all of those wear items at once. The performance friction module is the main upgrade: Raybestos material with more holding capacity than a standard rebuild set, so the forward and direct packs are less likely to slip and glaze under a heavy trailer or a hard launch. New steels give the frictions a flat, fresh surface, and new bushings take up the radial play that worn units develop at the pump, drums and shafts.
Pull the pan and read what is in it. Friction lining and black sludge mean burnt clutches, which this kit covers. Brass flakes point at bushings, also in the kit. Large steel chunks or broken roller clutch pieces mean hard-part damage, such as a cracked drum or failed planetary, which you will need to source separately. A line pressure test helps separate a leaking circuit from a sticking valve or worn pump, and our TH400 common problems guide walks through those checks. If the shifts are erratic rather than slipping, the TH400 valve body testing guide may point you somewhere cheaper.
The kit is listed for all GM TH400 and 3L80 transmissions from 1965 to 1996, which covers Chevrolet, GMC, Buick, Oldsmobile and Pontiac cars, C/K pickups, G-series vans and motorhomes. GM made running changes over those years, including different clutch plate counts by model code and early versus late pumps and center supports, so lay the new frictions and steels next to the old ones before assembly, and send us your year and VIN if you are unsure. Our TH350 vs TH400 guide helps confirm which unit you have. More parts are in the TH400 collection.
Soak the frictions in Dexron-type ATF before assembly, install lip seals facing the pressure side and lube sealing rings with assembly gel. Press the new bushings in square and check fit on their shafts. Set the clutch clearances and air-check every piston and servo before the valve body goes on. Sonnax points out that two of the four TH400 endplay checks are not in GM's procedure, and skipping them is a common cause of gear train failure, so measure all four. Inspect hard parts you reuse; a worn drum or TH400 pump will undo the new clutches. If the case snap ring groove is worn, a billet case saver snap ring support is worth adding for high-power builds.
| Fits | TH400 1965-1996 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | GM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is a master kit. Along with the overhaul gaskets and seals it includes a Raybestos performance friction module, a full steel module, high-energy bands, bushings and a filter.
Yes. GM renamed the TH400 to 3L80 for 1987, and the kit is listed for TH400 and 3L80 transmissions from 1965 through 1996.
Yes. The upgraded friction module has more holding capacity than a standard kit, which suits towing, street performance and higher-torque builds.
Inspect the drums, pump, planetary sets and roller clutches. Any cracked or worn hard part should be replaced, and the torque converter should be cleaned or replaced so old debris does not end up in the new clutches.
Use Dexron-type automatic transmission fluid. Soak the frictions in the same fluid before assembly.
