Torque Converters Notes

Torque Converters

1. Learning Objectives

  • 6.1 Identify and describe the components of a torque converter.
  • 6.2 Explain torque converter operation.
  • 6.3 Discuss the parts and operation of torque converter clutches.
  • 6.4 Describe the purpose and procedure of a stall test.
  • 6.5 Discuss the service of torque converters.

2. Torque Converter Components

  • Major Parts:
    • Turbine: Located on the engine side, drives the transmission.
    • Impeller: The driving member that rotates with the engine, located on the transmission side.
    • Stator: Mounted on a one-way clutch, acts as the reaction member.
  • Fluid Dynamics:
    • Impeller vanes pick up fluid from the converter housing and direct it towards the turbine, facilitating power transfer.

3. Torque Converter Operation

  • Hydrodynamic Unit:
    • Transfers power through the dynamic motion of fluid rather than static pressure, ensuring torque multiplication and coupling.
  • Fluid Flow Types:
    • Rotary Flow: Fluid circulates around the converter.
    • Vortex Flow: Fluid interacts with the guide rings, creating a vortex.

4. Torque Converter Clutches (TCC)

  • Purpose:
    • Eliminate slippage during the coupling phase, improving fuel economy.
  • Structure:
    • Made up of a large clutch disc, pressure plate, and damper assembly.
  • Operation:
    • Fluid is directed to engage the clutch, which connects the engine and transmission more directly, enhancing performance.

5. Stall Test

  • Purpose: Check the function of the stator one-way clutch and apply devices.
  • Procedure:
    1. Connect a scan tool to monitor RPM.
    2. Secure the vehicle and start the engine.
    3. Apply brakes and shift to reverse/throttle to wide open.
    4. Run engine at fast idle after shifting to neutral.
    5. Repeat previous steps with gear selector in drive and low.
  • Caution: Incorrect application can severely damage the transmission.

6. Torque Converter Service

  • Inspection Aspects:
    • Visual inspection, stator one-way clutch operation, turbine end play, lock-up clutch functioning, and any external leaks.
  • Service Integration:
    • Torque converters should be serviced or replaced during transmission overhaul.

7. Frequently Asked Questions

  • What Controls Torque Converter Clutch?
    • Controlled by the PCM through a de-energized solenoid adding or exhausting fluid pressure based on engine conditions (throttle position, load).
  • What is a Squashed Converter?
    • An elliptical cross-sectional converter design that reduces size for fitting in compact spaces, offering efficiency without sacrificing function.
  • High-Stall Speed Converter:
    • Defines how fast the engine RPM can increase before the turbine begins to turn; balancing performance to avoid excessive slippage is crucial.

8. Troubleshooting & Checks

  • Leaks and Damage Checks:
    • Inspect for leaks using specific fixtures and check for spline damage.
  • Stator Functionality Check:
    • Ensure splines rotate in one direction only, verify play through physical inspection.

9. Installation of Higher Stall Speed Converter

  • Steps Include:
    • Removing various components to access the converter.
    • Inspecting and replacing seals and ensuring proper fit with new components.
    • Final verification of the new converter's stall speed once installed.

10. Conclusion

  • Understanding torque converters is essential for diagnosing and servicing automatic transmissions effectively, emphasizing the importance of each component within the system.