Description: The torque converter
portion has the ability to multiply torque from the engine. The
impeller (sometimes called the pump) has specially curved vanes and
is driven by the engine's crankshaft. The turbine also has specially
curved vanes and is connected to the input shaft of the
transmission. Adding a third element, the stator (also called the
reactor), gives the assembly the capability it's named for. The
stator has vanes and is mounted on a one-way clutch, to allow it to
freewheel in only one direction. The stator assembly is located
between the impeller and turbine and redirects oil that bounces back
off the turbine. The force of the redirected oil assists in rotating
the turbine, resulting in torque multiplication. When the impeller's
speed is high and turbine's speed is low, torque can be multiplied
by as
much as 2:1. When the impeller's speed and
the turbine's speed are about
the same, torque can be transferred at
almost 1:1. Carmakers took the torque converter one step further by adding a
lock-up function beginning around 1980. Lock-up converters also contain a
friction clutch
that locks
the converter impeller to the turbine, usually in higher gears.
A solenoid-controlled oil passage, commanded by the car’s powertain control module
(PCM), locks and unlocks the converter based on driving
conditions.
Purpose: The torque converter,
connected to the transmission/transaxle input shaft, connects,
multiplies and interrupts the flow of engine torque into the
transmission. The torque converter supplies torque to the
transmission's input shaft in two separate, distinct ways: hydraulic
input and mechanical input (lock-up converters only). Hydraulic
input comes from the torque converter’s turbine and the amount of
input torque can vary depending on
the
operating conditions within the converter. Mechanical input results
when the lock-up function of the converter engages. The
end result is better
fuel economy because all converter slippage is eliminated when the
converter locks. The torque converter also helps to smooth out engine
power pulses, as does the flywheel on a car with a
manual transmission.
Maintenance Tips/Suggestions: The torque converter does not require any
regular maintenance or adjustments, but it may be possible to change
the transmission fluid in the converter through draining (if
equipped with a drain) or with
a transmission flushing and filling machine. Much of the transmission’s fluid
stays in the converter and since the converter produces a
tremendous amount of heat (the enemy of transmission fluid)
there’s good reason to change it if possible. Torque converter problems fall
into two categories: 1) problems within the torque converter itself,
or 2) problems within the torque converter
clutch. If you suspect a problem with the converter or
transmission, have it evaluated by a qualified
transmission specialist. With the complexity of today’s transmissions and torque
converters, there’s no room for guesswork.
