The Five Essential Components of a Torque Converter

The five primary components of a modern automotive torque converter are the impeller (pump), turbine, stator with a one-way clutch, lock-up clutch, and the automatic transmission fluid (ATF). Together, these elements transfer and multiply engine torque to the transmission in automatic vehicles, smoothing launches from a stop and improving efficiency at cruising speeds.

The Five Core Components Explained

The list below outlines each major component found in most contemporary, lock-up–type torque converters and explains what it does within the hydraulic coupling.

• Impeller (Pump): Connected to the engine via the converter cover; it slings ATF outward by centrifugal force, creating fluid flow and pressure that initiate torque transfer.
• Turbine: Splined to the transmission input shaft; it receives the fluid energy from the impeller and converts it back into rotational motion to drive the gearbox.
• Stator (with one-way clutch): Positioned between the impeller and turbine; it redirects fluid returning from the turbine, increasing flow efficiency and multiplying torque at low speeds. Its sprag/roller clutch locks at low turbine speed and freewheels at higher speeds.
• Lock-up clutch: A friction clutch inside the converter that mechanically links the impeller cover to the turbine at cruise, eliminating slippage to improve fuel economy, reduce heat, and sharpen drivability.
• Automatic transmission fluid (ATF): The working medium; transmits energy hydraulically, provides cooling and lubrication, and enables clutch operation. Without fluid in the correct spec and quantity, the converter cannot function.

Taken together, these parts create a fluid coupling that can multiply torque during launch and then transition to an efficient, near-direct mechanical connection at speed.

How These Components Work Together

The torque converter’s behavior changes with vehicle speed and load. Here’s the typical sequence of events from a standstill to highway cruising.

1. At idle/launch, the impeller spins with the engine, accelerating ATF outward; the turbine initially lags, creating high relative fluid velocity.
2. Returning fluid strikes the stator, which is locked by its one-way clutch; the stator redirects flow to assist the impeller, yielding torque multiplication for stronger launches.
3. As vehicle speed rises, turbine speed approaches impeller speed; the stator’s one-way clutch freewheels, reducing multiplication and acting as a simple fluid coupling.
4. At steady cruise, the lock-up clutch engages, mechanically linking impeller and turbine to cut slip, heat, and fuel consumption.
5. Throughout, the ATF carries energy, removes heat, and lubricates bearings and clutch surfaces.

This progression balances smoothness at low speed with efficiency at higher speeds, which is why modern automatics feel both refined and responsive.

Why This Matters for Drivers and Technicians

Common symptoms tied to specific components

The following points link typical drivability issues to the component most likely involved, helping with quick diagnosis.

• Shudder at light cruise often indicates lock-up clutch contamination or wear (old ATF, glazing, or control solenoid issues).
• Sluggish takeoff can point to stator one-way clutch failure (loss of torque multiplication) or low/incorrect ATF level.
• Overheating frequently traces to degraded or insufficient ATF, impeller vane damage, or towing beyond rating.
• Whine or growl noises may suggest bearing wear within the converter, pump cavitation from low ATF, or turbine/impeller damage.

Addressing fluid condition and level is the first, least invasive step; persistent issues may require converter replacement or transmission service.

Notes on variations in design

While the five elements above define most units, designs vary. Heavy-duty and modern high-efficiency converters may use multi-plate lock-up clutches, different stator blade geometry, and specialized low-viscosity ATF formulations. Dual-clutch and some hybrid transmissions do not use torque converters at all.

Summary

A torque converter’s five key components—impeller (pump), turbine, stator with one-way clutch, lock-up clutch, and ATF—work in concert to multiply torque at launch, smooth power delivery, and improve efficiency at cruise. Understanding each part’s role helps diagnose issues and maintain reliable, efficient operation in automatic transmissions.

What is inside a torque converter?

A torque converter contains an impeller connected to the engine, a turbine linked to the transmission’s input shaft, and a stator to redirect fluid and multiply torque. These components are housed in the converter’s casing and operate within a bath of transmission fluid. Many modern torque converters also feature a lock-up clutch that engages to create a direct mechanical connection at higher speeds, eliminating slippage.
 
This video provides an overview of the internal components of a torque converter: 41sTransmissions America (John and Eddie) YouTube · May 8, 2023
Here are the main components and their functions:

• Impeller (or Pump): This is a wheel with curved fins that is welded to the converter’s housing and connected to the engine’s flywheel. As the engine spins, the impeller flings transmission fluid outward with centrifugal force, transferring power. 
• Turbine: Located opposite the impeller, this component is connected to the transmission’s input shaft. The high-pressure fluid from the impeller strikes the turbine’s angled blades, causing it to spin and drive the transmission. 
• Stator: Positioned between the impeller and the turbine, the stator is equipped with a one-way clutch or sprag clutch. It redirects the fluid returning from the turbine back to the impeller, increasing its pressure and multiplying the engine’s torque, especially at low speeds. 
• Lock-Up Clutch: Found in many modern converters, this clutch assembly is attached to the turbine and can be hydraulically engaged. When engaged, it locks the turbine directly to the converter housing, creating a direct drive to the transmission and improving fuel efficiency by eliminating slippage. 
• Transmission Fluid: This incompressible fluid acts as the medium for transferring power between the impeller and the turbine, similar to how air transfers power between two fans. 
• Bearings and Seals: Various bearings and seals within the torque converter ensure smooth rotation of its components and prevent fluid from escaping. 

This video explains the basic operation of a torque converter: 44sSabin Civil EngineeringYouTube · Apr 13, 2018

What are the components of a converter?

The basic components of the converters are diodes, transistors and thyristors. – Cyclo-converter – A cyclo-converter is a single-stage (AC-AC) converter and converts AC with a constant frequency directly to an AC with a varying frequency, as required for the desired motor speed.

What are the basics of a torque converter?

A torque converter consists of three major internal components: the pump, turbine, and stator, as well as transmission fluid. The housing of the converter is bolted to the engine’s flywheel, and the fins of the pump are attached to the housing.

What are the 5 main parts of a torque converter?

In an automatic transmission car, the torque converter connects the power source to the load. Torque converters are comprised of five main components: the impeller, the turbine, the stator, a clutch, and the fluid.