The fluid coupling was widely used on early auto-
matic transmissions. Fluid couplings, however, slip exces-
sively and are very inefficient at transmitting power at low
speeds. Therefore, fluid couplings have been replaced by
torque converters. In addition to an impeller and a turbine,
a torque converter uses a device called a stator. The stator
redirects the fluid to reduce slipping, Figure 1-15. All
transmissions made since the 1960s use torque converters.
Modern transmissions are equipped with lockup
torque converters. These torque converters are equipped
with an internal clutch called a converter lockup clutch.
The converter lockup clutch locks the transmission input
shaft to the converter cover. The clutch is applied to lock
the turbine to the cover. Since the input shaft is attached to
the turbine, slippage is eliminated. The lockup clutch is
disengaged at low speeds to prevent engine stalling.
18 Automatic Transmissions and Transaxles
Input
shaft
Torque converter
Converter
housing
Pump and
reactor support
Pump
gasket
Selective thrust washers
Intermediate
band
Output shaft
hub and ring
gear assembly
Reverse planet
Sun gear
Input shell
Front planet
Reverse
high clutch
Forward
clutch
Forward clutch
hub and ring
gear assembly
Throttle valve
Remove as
assembly
Low-reverse
drum
Low-reverse
band
Inner
race
Rollers
Cage spring
Outer race
One-way clutch
Case
Low-reverse
servo
TV rod
Diaphragm
Collector
body
Governor
Distributor
sleeve
Park gear
Parking pawl
and spring
Vent cap
Output
shaft
Valve
body
Filter
screen
Extension
housing
and gasket
Pan gasket
Oil pan
Figure 1-12. Exploded view of a typical automatic transmission. (Ford)