8HP70 Input Drum, used and ready to install. Fits the 8HP70. Ships fast from the USA.
This listing is the input shaft for the ZF 8HP70 and 8HP55 eight-speed automatics, not a clutch drum. It is a good used shaft, 20.5 inches overall, with 32 splines at the front for the torque converter and a 1.745 inch spline diameter where it drives the second planetary gearset. Shops look for one when a teardown finds stripped converter splines, a shaft scored where its sealing rings ride, or damage after a converter or bushing failure. It fits BMW, Ram, Jeep, Dodge, Chrysler and Audi applications built around those two cases.
The 8HP gets eight forward gears out of four simple planetary gearsets and five shift elements: two brakes, A and B, and three clutches, C, D and E. Every bit of engine torque that leaves the converter turbine enters the gear train through this shaft. Its front splines take the turbine hub, and its rear splines turn the planetary set it is tied to. Along its length are machined lands for sealing rings that pass pressurized fluid to the rotating clutches and the converter. If a land wears or a ring groove gets chewed up, oil leaks across the circuit before it reaches the piston, and the clutch it feeds gets less apply pressure than the mechatronic commands. The Sonnax TorqueFlite 8 theory material lays out which element is on in each gear, which helps you tell from a slip pattern whether a shaft-fed circuit is the likely leak.
Start with the fluid. BMW's own 8HP diagnosis bulletin has the technician check the level on every complaint before going further, and the 8HP level has to be set hot within a set temperature window with the engine running. A low unit can act like a slipping one. Then scan for codes and watch input and output speeds. If the engine and turbine speeds climb but the output never moves, the drive is broken inside. Our ZF8HP common problems guide and the BMW 3 Series 8HP problems guide cover faults that look like this one, such as mechatronic sleeve leaks and valve body wear, so you do not pull the transmission for a pressure leak that sits in the valve body. If you do pull the unit, inspect both spline sets and every seal land before you order.
The source listing gives this shaft for the 8HP55 and 8HP70 only. Those are first-generation 8HP cases. The 8HP50, 8HP75 and 8HP95 that followed are second-generation units, and you should not assume a first-generation shaft fits them. Before you buy, match your old shaft: overall length (20.5 inches), converter spline count (32) and the rear spline size. Or send us the transmission ID tag, year and VIN. Other 8HP parts are on our ZF 8HP parts page.
After the rebuild, reset the transmission adaptations with a capable scan tool and drive the unit gently through every gear so the mechatronic can learn the new clutch clearances.
| Fits | 8HP70 |
| 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.
It is the input shaft. The listing name says drum, but the part is a used 8HP55/8HP70 input shaft, 20.5 inches long, with 32 converter splines. If you need a clutch drum, see our separate 8HP70 clutch drum listing.
Do not assume it will. This shaft is listed for the first-generation 8HP55 and 8HP70. The 8HP50, 8HP75 and 8HP95 are second-generation cases. Compare length and spline counts with your old shaft, or send us your transmission tag and VIN.
It can be. A stripped shaft or converter spline gives exactly that symptom. Check fluid level and codes first, though. A very low level or a mechatronic fault can also leave you with no drive.
Install new sealing rings on the shaft, and check the bushings and bores it runs in. If the splines failed, inspect the converter hub. Most shops do this during a full rebuild with a master kit, a new filter and fresh LifeguardFluid 8.
Yes. Reset the adaptations with a scan tool after the rebuild. Set the fluid level hot using the ZF procedure, then drive through all gears so the controller relearns the shifts.
