Boone County ATC Diesel Technology DIT150: Powertrain Mr. Hillenbrand Spring 2015 Torque Converters

Objectives Outline the function of the torque converter in a vehicle equipped with an automatic transmission. Explain how the torque converter is coupled between the crankshaft and the transmission. Identify the three main elements of a torque converter torus and describe their roles.

( Objectives cont.) Define torque multiplication and explain how it is generated in the torque converter. Define both rotary and vortex fluid flow and explain how each affects torque converter operation. Describe the overrunning clutch, lockup clutch, and variable pitch stators.

( Objectives cont.) Outline torque converter service and maintenance checks. Remove, disassemble, inspect, and reassemble torque converter components.

INTRODUCTION Fully automatic truck (and passenger car) transmissions use a type of fluid coupling known as a torque converter to transmit engine torque to the transmission. The coupling agent is fluid. Because it is a fluid coupling, some element of forgiveness between input and output speeds is provided.

OPERATING PRINCIPLE A torque converter transmits twisting force hydraulically using automatic transmission fluid, often simply called transmission oil. The role of a torque converter is to transmit or multiply the twisting force or torque delivered to it by the engine crankshaft. It then directs torque through to the transmission to provide a number of ratios suitable for the particular load and speed of the vehicle.

TORQUE CONVERTER LOCATION

FLEXPLATE

TORQUE CONVERTER COMPONENTS

T/C Exterior

Operation

PRINCIPLES OF OPERATION

Shop Talk There can be a mechanical connection between the impeller and turbine by the use of a lockup clutch. A lockup clutch eliminates slippage between the impeller and turbine at certain speeds. This helps to reduce the heat generated in the fluid and improves fuel mileage.

TYPES OF OIL FLOW

SPLIT GUIDE RINGS

Torque Multiplication

Overrunning Clutch

Variable Pitch Stator

LOCKUP CLUTCHES

REMOVING THE TRANSMISSION/ TORQUE CONVERTER

CAUTION! The T/C is free to move forward when the transmission is disconnected from the engine. To ensure that the T/C does not separate from the transmission while the transmission is being removed from the vehicle, install a retaining strap to hold the T/C in position.

Pressure Testing (Sealed/Welded Units)

CAUTION! Exhaust the air pressure at the test valve stem before loosening the nut holding the test fixture in place.

Check Endplay

TORQUE CONVERTER DISASSEMBLY

Shop Talk If it is necessary to rebuild the stator assembly, remove the needle bearing assembly before starting the stator rebuild. Always follow the T/C manufacturer’s rebuild procedures for all T/C subassemblies. Do not disassemble the stator assembly unless parts replacement is needed.

CAUTION! Apply load only to the outer shell of the bearing during installation.

Flywheel Assembly

Lockup Clutch Back Plate

Turbine Assembly

Lockup Clutch Piston.

Stator

Pump/Impeller

Pump (Impeller) Hub

SUMMARY Automatic truck (and passenger car) transmissions use a type of fluid coupling known as a torque converter to transfer engine torque from the engine to the transmission. A flexplate, sometimes called a flex disc, is used to connect the torque converter to the crankshaft

Summary (cont.) Transmission oil is used as the medium to transfer energy from the engine-driven impeller to the turbine, which in turn drives the transmission. Two types of oil flow take place inside the torque converter: rotary flow and vortex flow. A converter lockup clutch enables a mechanical coupling of the engine and transmission.

Any Questions ?