Jeep XJ. Manual — part 391
TORQUE CONVERTER CLUTCH (TCC)
The TCC (Fig. 14) was installed to improve the
efficiency of the torque converter that is lost to the
slippage of the fluid coupling. Although the fluid cou-
pling provides smooth, shock–free power transfer, it
is natural for all fluid couplings to slip. If the impel-
ler and turbine were mechanically locked together, a
zero slippage condition could be obtained. A hydraulic
piston was added to the turbine, and a friction mate-
rial was added to the inside of the front cover to pro-
vide this mechanical lock-up.
OPERATION
The converter impeller (Fig. 15) (driving member),
which is integral to the converter housing and bolted
to the engine drive plate, rotates at engine speed.
The converter turbine (driven member), which reacts
from fluid pressure generated by the impeller, rotates
and turns the transmission input shaft.
TURBINE
As the fluid that was put into motion by the impel-
ler blades strikes the blades of the turbine, some of
the energy and rotational force is transferred into the
turbine and the input shaft. This causes both of them
(turbine and input shaft) to rotate in a clockwise
direction following the impeller. As the fluid is leav-
ing the trailing edges of the turbine’s blades it con-
tinues in a “hindering” direction back toward the
impeller. If the fluid is not redirected before it strikes
the impeller, it will strike the impeller in such a
direction that it would tend to slow it down.
STATOR
Torque multiplication is achieved by locking the
stator’s over-running clutch to its shaft (Fig. 16).
Under stall conditions (the turbine is stationary), the
oil leaving the turbine blades strikes the face of the
stator blades and tries to rotate them in a counter-
clockwise direction. When this happens the over–run-
ning clutch of the stator locks and holds the stator
from rotating. With the stator locked, the oil strikes
the stator blades and is redirected into a “helping”
direction before it enters the impeller. This circula-
tion of oil from impeller to turbine, turbine to stator,
and stator to impeller, can produce a maximum
torque multiplication of about 2.4:1. As the turbine
begins to match the speed of the impeller, the fluid
that was hitting the stator in such as way as to
cause it to lock–up is no longer doing so. In this con-
dition of operation, the stator begins to free wheel
and the converter acts as a fluid coupling.
TORQUE CONVERTER CLUTCH (TCC)
In a standard torque converter, the impeller and
turbine are rotating at about the same speed and the
Fig. 13 Stator Location
1 – STATOR
2 – IMPELLER
3 – FLUID FLOW
4 – TURBINE
Fig. 14 Torque Converter Clutch (TCC)
1 – IMPELLER FRONT COVER
2 – THRUST WASHER ASSEMBLY
3 – IMPELLER
4 – STATOR
5 – TURBINE
6 – FRICTION DISC
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AUTOMATIC TRANSMISSION—30RH
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DESCRIPTION AND OPERATION (Continued)
stator is freewheeling, providing no torque multipli-
cation. By applying the turbine’s piston to the front
cover’s friction material, a total converter engage-
ment can be obtained. The result of this engagement
is a direct 1:1 mechanical link between the engine
and the transmission.
The engagement and disengagement of the TCC
are automatic and controlled by the Powertrain Con-
trol Module (PCM). The engagement cannot be acti-
vated in the lower gears because it eliminates the
torque multiplication effect of the torque converter
necessary for acceleration. Inputs that determine
clutch engagement are: coolant temperature, vehicle
speed and throttle position. The torque converter
clutch is engaged by the clutch solenoid on the valve
body. The clutch will engage at approximately 56
km/h (35 mph) with light throttle, after the shift to
third gear.
OIL PUMP
DESCRIPTION
The oil pump (Fig. 17) is located in the pump hous-
ing inside the bell housing of the transmission case.
The oil pump consists of an inner and outer gear, a
housing, and a cover that also serves as the reaction
shaft support.
Fig. 15 Torque Converter Fluid Operation
1 – APPLY PRESSURE
2 – THE PISTON MOVES SLIGHTLY FORWARD
3 – RELEASE PRESSURE
4 – THE PISTON MOVES SLIGHTLY REARWARD
Fig. 16 Stator Operation
1 – DIRECTION STATOR WILL FREE WHEEL DUE TO OIL
PUSHING ON BACKSIDE OF VANES
2 – FRONT OF ENGINE
3 – INCREASED ANGLE AS OIL STRIKES VANES
4 – DIRECTION STATOR IS LOCKED UP DUE TO OIL PUSHING
AGAINST STATOR VANES
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AUTOMATIC TRANSMISSION—30RH
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DESCRIPTION AND OPERATION (Continued)
OPERATION
As the torque converter rotates, the converter hub
rotates the inner and outer gears. As the gears
rotate,
the
clearance
between
the
gear
teeth
increases in the crescent area, and creates a suction
at the inlet side of the pump. This suction draws
fluid through the pump inlet from the oil pan. As the
clearance between the gear teeth in the crescent area
decreases, it forces pressurized fluid into the pump
outlet and to the valve body.
VALVE BODY
DESCRIPTION
The valve body consists of a cast aluminum valve
body, a separator plate, and transfer plate. The valve
body contains valves and check balls that control
fluid delivery to the torque converter clutch, bands,
and frictional clutches. The valve body contains the
following components (Fig. 18) and (Fig. 19):
• Regulator valve
• Regulator valve throttle pressure plug
• Line pressure plug and sleeve
• Kickdown valve
• Kickdown limit valve
• 1–2 shift valve
• 1–2 control valve
• 2–3 shift valve
• 2–3 governor plug
• Throttle valve
• Throttle pressure plug
• Switch valve
• Manual valve
• Converter clutch control valve
• Fail-safe valve
• Shuttle valve
• Shuttle valve throttle plug
• 9 check balls
By adjusting the spring pressure acting on the reg-
ulator valve, transmission line pressure can be
adjusted.
OPERATION
NOTE: Refer to the Hydraulic Schematics for a
visual aid in determining valve location, operation
and design.
Fig. 17 Oil Pump Assembly
1 – OIL SEAL
2 – OIL PUMP BODY
3 – VENT
4 – REACTION SHAFT SUPPORT
5 – INNER ROTOR
6 – OUTER ROTOR
7 – “O” RING
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DESCRIPTION AND OPERATION (Continued)
REGULATOR VALVE
The pressure regulator valve is needed to control
the hydraulic pressure within the system and reduce
the amount of heat produced in the fluid. The pres-
sure regulator valve is located in the valve body near
the manual valve. The pressure regulator valve train
controls the maximum pressure in the lines by
metering the dumping of fluid back into the sump.
Regulated pressure is referred to as “line pressure.”
The regulator valve (Fig. 20) has a spring on one
end that pushes the valve to the left. This closes a
dump (vent) that is used to lower pressure. The clos-
ing of the dump will cause the oil pressure to
increase. Oil pressure on the opposite end of the
valve pushes the valve to the right, opening the
dump and lowering oil pressure. The result is spring
pressure working against oil pressure to maintain
the oil at specific pressures. With the engine run-
ning, fluid flows from the pump to the pressure reg-
ulator valve, manual valve, and the interconnected
circuits. As fluid is sent through passages to the reg-
ulator valve, the pressure pushes the valve to the
right against the large spring. It is also sent to the
reaction areas on the left side of the throttle pressure
plug and the line pressure plug. With the gear selec-
tor in the park position, fluid recirculates through
the regulator and manual valves back to the sump.
Fig. 18 Valve Body Assembly
1 – GOVERNOR PLUG END PLATE
2 – SHUTTLE VALVE
3 – 1–2 GOVERNOR PLUG
4 – VALVE BODY
5 – REGULATOR VALVE THROTTLE PRESSURE PLUG
6 – SLEEVE
7 – LINE PRESSURE PLUG
8 – RETAINER
9 – 1–2 SHIFT VALVE
10 – 1–2 SHIFT CONTROL VALVE
11 – KICKDOWN LIMIT VALVE
12 – END PLATE
13 – THROTTLE PRESSURE PLUG
14 – KICKDOWN LIMIT VALVE BODY
15 – E-RING
16 – 2–3 SHIFT VALVE
17 – GUIDES
18 – 2–3 GOVERNOR PLUG
19 – PRIMARY SPRING
20 – SHUTTLE VALVE THROTTLE PLUG
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AUTOMATIC TRANSMISSION—30RH
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DESCRIPTION AND OPERATION (Continued)
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