TH400 Overhaul Kit 1965-1987, new and ready to install. Fits the TH400. Ships fast from the USA.
If your Turbo 400 is already on the bench, or you are about to pull it because of leaks, a slow engagement on a cold start or a shift that has gone soft, the first thing on the parts list is the soft-parts kit that every circuit seals against. This is the Precision International KP34900A overhaul kit, catalogued for the TH400 and the front-drive TH425 from 1965 through 1987. It suits the 400s found in Chevrolet, GMC, Buick, Oldsmobile, Pontiac and Cadillac cars and trucks of that era, and the same kit was catalogued for TH400-equipped Jeep, Jaguar, Rolls-Royce and Bentley applications.
It is a gasket and seal kit. It does not contain friction plates, steel plates, bands, bushings or a filter, so plan to buy the wear parts your teardown calls for separately.
The TH400 is a hydraulic 3-speed: a gear-type front pump makes line pressure, and that oil is routed through the pump cover and the center support to apply the forward, direct and intermediate clutches and the front and rear bands. The oil passes from stationary parts into spinning drums across sealing rings, and every piston relies on a lip seal or O-ring to hold apply pressure. Once those rings and seals harden or wear, pressure bleeds off inside the case, so a clutch that is still physically fine applies slowly and slips. The 1975 GM service manual lists leaking pump-cover and center-support oil rings as causes of slipping and of no-drive conditions, which is exactly what this kit renews.
Check fluid level and condition first. Burnt fluid and friction material in the pan mean the clutch packs are finished too, so you need frictions and steels in addition to this kit. A line pressure test with a gauge on the case tap tells you whether the pump and regulator are producing pressure; low pressure in one range only points at a leaking circuit seal. Our TH400 delayed engagement guide walks through the cold-engagement checks, and TH400 common problems and fixes covers the direct clutch and low roller clutch failures to inspect for while the unit is apart.
The kit is listed for TH400 and TH425 transmissions built from 1965 to 1987. The 400 changed in detail over that run, including pump and governor revisions and the electric detent solenoid, so check that your case, pump and valve body match the parts shown before opening the package, since opened soft-parts kits are generally not returnable. If you are unsure, send us your year, vehicle and VIN and we will confirm fit. Browse every part we carry for this transmission on the TH400 parts page.
If the transmission only leaks externally and shifts well, the lighter TH400 external reseal kit covers the pan, pump and rear seals without a full teardown.
| Fits | TH400 1965-1987 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | OEM |
| Reference | KP34900A |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It contains gaskets, lip seals, O-rings and sealing rings (ten metal and one Teflon). Frictions, steels, bands, bushings and the filter are separate purchases.
The kit is catalogued for TH400 and TH425 units from 1965 through 1987, which includes mid-1980s truck 400s. Compare your pump and valve body to the gaskets shown, or send us the year and VIN and we will check it.
The TH400 was designed for Dexron automatic transmission fluid. A modern Dexron-licensed ATF is the usual choice for refill.
Only if the slip comes from leaking seals or rings and the clutches are still good. If the fluid is burnt or the frictions are worn, replace the clutch packs together with this kit.
No. A front pump lip seal is included, along with the pump-to-case gasket and the rear seal, so the common leak points are covered while the unit is apart.
