TRUCK SERVICE MANUAL
TRANSMISSION
Para 2-5/2-8
DESCRIPTION AND OPERATION
b. Operation (B, foldout 7). The lockup shift valve
the direction of oil flow (when the stator is locked against
directs clutch apply pressure to the lockup clutch piston
rotation), and directs the oil to the pump in a direction
when sufficient rotational speed is achieved by the
that assists the rotation of the pump. It is the redirection
forward clutch and turbine shaft assembly. The clutch
of the oil in a manner to assist the pump that enables the
apply pressure compresses the lockup clutch plate
torque converter to multiply input torque.
between the piston and back plate, locking all three
(4) Greatest torque multiplication occurs when
together. Thus, the converter pump and turbine are
the turbine is stalled and the pump is rotating at its
locked together, and provide a direct drive from the
highest speed. Torque multiplication decreases as the
engine. As rotational speed of the forward clutch and
turbine rotates and gains speed.
shaft assembly decreases, the lockup shift valve will
release the lockup clutch.
(5) When turbine speed approaches the
speed of the pump, oil flowing to the stator begins
2-7. TORQUE CONVERTER HOUSING
striking the backs of the stator vanes.
Converter housing 16 (A, foldout 8) is machined from
This rotates the stator in the same direction as the
cast aluminum. The front of the housing is machined to
turbine and pump. At this point, torque multiplication
mate with an SAE 1 engine flywheel housing. The rear
stops and the converter becomes, in effect, a fluid
of the housing is machined to accept either retarder plate
coupling.
assembly 2 or 19 (A, foldout 10), or front support and
valve assembly 1 or 30 (B, foldout 10), and transmission
(6) Thus, as explained in (1) through (5),
housing 7 (A, foldout 14). The converter housing
preceding, the torque converter accomplishes three main
encloses and supports the torque converter elements
functions. It acts as a disconnect clutch because little
and input-driven oil pump assembly 1 (A, foldout 8).
torque is transmitted at engine idle speed. It multiplies
torque at low turbine/high pump speed to give greater
2-9. OIL PUMP ASSEMBLY
starting or driving effort when needed. It acts as a fluid
coupling to efficiently transmit engine torque to the
a. Description (A, foldout 8). Oil pump assembly 1
transmission gearing during drive, other than idle or
consists mainly of three elements drive gear 4, d r iv e n
starting.
gear 7 and pump body 3. The oil pump assembly is
2-6. LOCKUP CLUTCH
a. Description (B, foldout 7). The lockup clutch
consists mainly of three elements piston 3, clutch plate 4,
and back plate 5. These elements a r e located inside
the flywheel. The piston and back plate rotate with the
converter pump. The clutch plate is located between the
piston and back plate and is splined to the converter
turbine.
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