TH400 Input Drum 1974-1979, used and ready to install. Fits the TH400. Ships fast from the USA.
A Jeep with a Turbo 400 that has Reverse but will not pull in Drive, or that slips in every forward gear once it warms up, usually has a problem in the forward clutch. This listing is the forward clutch drum with its input (turbine) shaft, pulled from a 1974-1979 Jeep TH400 used in the CJ-7, Wagoneer and J10 pickup. It is a used original part in fair shape, removed from a working transmission with no reported issues, and it is sold as removed, not cleaned or machined.
The torque converter turbine drives the TH400 through this assembly. The turbine shaft splines into the converter at the front and into the forward clutch housing at the rear, so every bit of engine torque headed for the gear train passes through it. Inside the housing are the forward clutch piston, sixteen release springs and, in the 1975 GM manual, a pack of five radial-groove frictions, four flat steels and one waved steel. The forward clutch is applied in all three forward gears, which is why a leak or worn pack here hits first, second and third at once while Reverse can still work. The rear of the housing also carries the direct clutch hub, held by a snap ring.
GM's 1975 diagnosis chart lists a damaged, stuck or missing check ball in the forward clutch housing, a cracked piston, bad piston seals and low line pressure as the causes of burned forward clutch plates. Any of those will kill a new friction pack, so they are worth ruling out on the old drum.
Check the fluid level with the engine running, then confirm line pressure with a gauge. A worn pump or leaking pump-cover sealing rings starve the forward clutch and mimic a bad drum, which our TH400 pump failure guide explains. If pressure is good and the truck has Reverse but no Drive, the forward circuit is the likely cause. For slow engagement after the Jeep sits overnight, read the TH400 delayed engagement guide first.
This drum and shaft came out of a TH400 from a 1974-1979 Jeep, the years Jeep used the GM unit behind its AMC six and V8 engines, often paired with the full-time Quadra-Trac transfer case, before switching to the Chrysler 727 after 1979. The internal forward clutch parts are shared with other TH400s, but turbine shaft length and spline count are what decide fitment, so lay this shaft next to the one you pull and compare them, or send us your year and VIN before ordering. If you need a non-Jeep or reman unit, see our TH400 input drum 1964-1990 or browse the TH400 parts collection.
Because this drum is sold as removed, plan to tear it down: pull the snap ring, direct clutch hub and forward hub, then clean the housing and every oil passage. Check that the check ball in the housing moves freely, inspect the ground bushing journals on the shaft and the lube holes at each end, and replace the piston seals with lips facing away from the spring pockets. Reinstall the bronze thrust washer on the side of the forward hub facing the housing, stack the plates starting with the waved steel, and air-check the piston. Fill with Dexron-type ATF. A seal set like the TH400 overhaul kit 1966-1991 or a full TH400 banner rebuild kit with frictions covers the soft parts this drum needs.
| Fits | TH400 1974-1979 |
| Part type | Input Drum |
| Condition | Used |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes. On the TH400 the input drum is the forward clutch housing, and this one comes with the turbine (input) shaft installed.
The forward clutch housing internals are shared across TH400s, but the turbine shaft is what has to match. Compare overall length and spline count with your old shaft, or send us your year and VIN.
It is sold as removed from the transmission and not cleaned. Plan on new frictions, steels and seals during the rebuild rather than reusing what is inside.
It is a common cause, because the forward clutch applies in every forward gear but not in Reverse. Check fluid level and line pressure first so a weak pump is not mistaken for a bad drum.
Dexron-type automatic transmission fluid. Fill to the full mark on the dipstick with the engine running and the fluid at operating temperature.
