TH400 Clutch Drum 1964-1990, remanufactured and ready to install. Fits the TH400. Ships fast from the USA.
If your Turbo 400 has no Drive but still has Reverse, takes a long pause going from Neutral to Drive, or came apart with a burned front clutch pack, the forward clutch drum is the assembly you are shopping for. This listing is a TH400 forward drum assembly for 1964-1990 units: a good used factory forward clutch housing with the turbine shaft in it, built back up with five new Alto high energy frictions, six reconditioned steels, an aluminum piston, the sixteen release springs and spring retainer, the forward clutch hub, the direct clutch hub and the snap rings and washers that go with them. It drops into GM trucks, vans, motorhomes and the big cars that used the TH400 in that span.
The TH400 forward drum is the first rotating assembly behind the pump. The turbine shaft splines to the torque converter, so the housing turns at turbine speed all the time. When you select Drive, L2 or L1, oil fed through the pump stator sealing rings strokes the piston and clamps the forward pack, and the forward clutch hub then drives the mainshaft. That clutch is on in every forward gear, which is why a failed forward pack takes away all forward motion while Reverse, which runs through the direct clutch and rear band, can still work. The direct clutch hub is snap-ringed to the back of the housing, so the forward drum also delivers turbine torque into the direct clutch for third gear.
Check the fluid level and the manual linkage first, then put a gauge on the line pressure tap. GM's diagnosis chart for no drive in Drive range lists low fluid, linkage, low line pressure and the valve body ahead of the forward clutch, and a weak pump or a torn filter O-ring will mimic a dead clutch pack. If pressure is normal in Drive and the car still will not pull, the forward clutch is the next suspect: a cracked piston, damaged seals, a stuck or missing check ball in the housing, or broken pump sealing rings that feed the clutch. Our TH400 delayed engagement guide walks the pressure checks in order, and the TH400 common problems and fixes breakdown covers how the drums and roller clutches fail under added power.
This forward drum assembly is listed for TH400 transmissions from 1964 through 1990, which covers the Chevrolet, GMC, Buick, Oldsmobile, Pontiac and Cadillac applications of that era. GM did change details over the run: production forward pistons were aluminum or stamped steel, the THM 375 version used fewer plates, and turbine shaft length depends on the converter and case it came out of. Compare the turbine shaft length and spline count, and the bushing journals, against the drum you remove before you install it. If you are unsure, send us your year, vehicle and the transmission ID tag and we will check it. For the rest of the parts that fit your unit, shop the TH400 parts collection.
Because the forward pack is fed through the pump, a drum is only as good as the sealing rings and bushings in front of it. Replace the rest of the seals and soft parts with a TH400 overhaul kit, and if the pump bushing or stator rings are worn, look at a TH400 pump while the unit is apart. The TH400 pump failure guide explains what to check on the stator shaft.
| Fits | TH400 1964-1990 |
| Part type | Clutch Drum |
| Condition | Remanufactured |
| 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.
It is the forward clutch drum assembly: the forward clutch housing with the turbine shaft, forward clutch hub, direct clutch hub, piston, springs, new frictions and reconditioned steels. The direct clutch drum, which carries the intermediate sprag, is a separate part.
Reverse working with no Drive points at the forward clutch, but check fluid level, linkage and line pressure first. A pump that cannot make pressure or broken pump sealing rings will also stop the forward clutch from applying, and a new drum will not cure that.
The assembly is listed for 1964-1990 TH400 units, which includes that truck. Before installing, compare the turbine shaft length, spline count and bushing journals with the drum you remove, since shafts varied by application. Send us your year and transmission ID tag if you want us to check.
The TH400 uses Dexron ATF. Pre-soak the new frictions in the same fluid before assembly, and fill and check the level hot after the rebuild.
At minimum the pump stator sealing rings, gaskets and seals, plus the thrust washers. A full overhaul kit covers the soft parts, and the pump bushing should be checked because the forward clutch is fed through the pump.
Yes. Measure front unit end play at the turbine shaft after the pump is torqued. GM's spec is .003 to .024 inch, controlled by the selective washer between the pump and the forward clutch housing.
