Fluid CouplingTorque Multiplication

Torque converter purposes

• Allows vehicle to stop in gear

• Creates connection between engine and transmission

• When using locking converter a 1:1 link can be established

• Multiplies torque at low RPMs

Basic components

• Turbine

• Impeller

• Stator with one-way clutch

• Pressure plate if lock-up

Operation

• Impeller– Part of housing bolted

to flexplate

– Pumps fluid by centrifugal force

– Throws fluid out to contact turbine vanes

• Turbine– Locked to input shaft

– Acted on by force of fluid

– Spins faster based on fluid force

– Can only obtain 90% of impeller speed unless lockup style

Operation of stator

• Fluid flow can be re-directed to “help” impeller at lower speeds increasing torque of engine

• Fluid re-directing is performed by stator

• After torque multiplication is not desired stator overruns

• Defective one way clutch can cause lack of power at low or high rpm

Stall speed

• Stall speed is the point when engine rpm is limited by fluid pressure on turbine

• Controlled by vane design and stator

• Too low stall speed can indicate stator problems

• Too high can indicate slipping trans.

Torque converter facts

• Fluid for coupling is supplied by trans. pump through shaft

• Most of the heat is created in converter• Usually just before cooler• Not a serviceable unit• Can hold 10+ quarts of oil• Converter housing often drives trans. oil pump• Watch for loose bolts

Converter lock-up

• Performed by mechanically linking turbine to housing

• Controlled with hydraulics and electronics

• Has friction surface with a dampening pressure plate

• Used to increase mileage by reducing 10% slip

Lock-up problems

• Can stick on, causing stalling

• Can shutter on engagement

• Can cause chuggle

• Inop causing mileage complaints and or overheating trans.