Parts of a Torque Converter – 7 Parts Labeled, Cut Through

All 7 parts on the diagram

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Housing (cover) The sealed outer case, full of transmission fluid. Its front cover is bolted to the engine and turns with it.
Impeller (pump) Turns with the engine, built into the housing's rear shell. Its vanes throw fluid at the turbine.
Turbine Facing the impeller, its vanes are pushed round by the fluid. It turns the transmission input shaft.
Stator A small vaned wheel between the turbine and impeller. It turns the fluid coming back from the turbine so it helps the impeller, multiplying the engine's torque.
One-way clutch Holds the stator still while torque is being multiplied. Lets it freewheel forward once the turbine catches up with the impeller.
Lock-up clutch A friction disc that locks the turbine to the housing. It locks at cruising speed, so no power is lost to slipping fluid.
Input shaft The transmission input shaft, turned by the turbine. It carries the drive into the automatic transmission.

How this list was compiled: Read 2026-09-27. (1) US Army, TM 9-8000, Principles of Automotive Vehicles (1985), paragraphs 21-8 and 21-9 and figures 21-16 to 21-19, https://archive.org/details/tm-9-8000-principles-of-automotive-vehicles-1985 : the pump and the turbine, the stators that reverse the oil's direction and stand still while torque is multiplied, their freewheeling (overrunning) clutches that let them overrun when the turbine nears pump speed; the output shaft attached to the turbine; the frictional lock-up clutch that locks the turbine to the converter housing to end slippage at highway speed; the transmission input shaft. (2) Wikipedia, Torque converter, https://en.wikipedia.org/wiki/Torque_converter : the impeller driven by the engine, the turbine that drives the load, the stator between them on an overrunning (one-way) clutch; the lock-up clutch locking the turbine to the impeller; welded converter housings; the converter between the engine's flexplate and the transmission. Licence: own work

The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

How it works

These are the parts of a torque converter, which joins the engine to an automatic transmission, cut in half along its shaft with the engine side at the left.

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Drive through fluid

The housing turns with the engine, and the impeller in its rear shell throws fluid at the turbine's vanes. The turbine turns the transmission input shaft. With the car held on the brake, the turbine can stand still while the impeller turns.

More torque, then lock-up

The stator turns the fluid returning from the turbine so it helps the impeller, multiplying torque. Once the turbine catches up, the one-way clutch lets the stator freewheel. At cruising speed the lock-up clutch locks the turbine to the housing.

Impeller and pump are two names for the same part: the half that turns with the engine.

Questions and answers

What are the three main parts of a torque converter?

The impeller, driven by the engine; the turbine, which drives the transmission; and the stator between them, which multiplies torque.

What does the stator do in a torque converter?

It redirects the fluid coming back from the turbine so it pushes the impeller forward instead of against it. That is what lets a torque converter multiply torque, unlike a plain fluid coupling.

What is a lock-up clutch?

A friction clutch inside the converter that locks the turbine to the housing at cruising speed, ending the slip in the fluid and saving fuel.