Jeep XJ. Manual - part 388

2.5L engine (Fig. 1). The 30RH is three speed trans-
missions with a lock-up clutch in the torque con-
verter. The transmissions contain a front and rear
clutch which function as the input driving compo-
nents. They also contain the kickdown (front) and the
low/reverse (rear) bands which, along with the over-
running clutch, serve as the holding components. The
driving and holding components combine to select the
necessary planetary gear components, in the front
and rear planetary gear set, transfer the engine
power from the input shaft through to the output
shaft. The transmissions contain a governor that is
mounted on the output shaft and supplies pressure
to the valve body based on the output shaft speed.
The valve body is mounted to the lower side of the
transmission and contains the valves to control pres-
sure regulation, fluid flow control, and clutch/band
application. The oil pump is mounted at the front of
the transmission and is driven by the torque con-
verter hub. The pump supplies the oil pressure nec-
essary for clutch/band actuation and transmission
lubrication. The 30RH transmission is cooled by an
integral fluid cooler inside the radiator.

AUTOMATIC TRANSMISSION—30RH

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Fig. 1 30RH Automatic Transmission

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AUTOMATIC TRANSMISSION—30RH

DESCRIPTION AND OPERATION (Continued)

TRANSMISSION IDENTIFICATION

Transmission identification numbers are stamped

on the left side of the case just above the oil pan gas-
ket surface (Fig. 2). Refer to this information when
ordering replacement parts.

TRANSMISSION GEAR RATIOS

Forward gear ratios are:
• 2.74:1 (first gear)

• 1.54:1 (second gear)

• 1.00:1 (third gear)

OPERATION

The application of each driving or holding compo-

nent is controlled by the valve body based upon the
manual lever position and governor pressure. The
governor pressure is a variable pressure input to the
valve body and is one of the signals that a shift is
necessary. First through third gear are obtained by
selectively

applying

and

releasing

the

different

clutches and bands. Engine power is thereby routed
to the various planetary gear assemblies which com-
bine with the overrunning clutch assembly to gener-
ate the different gear ratios. The torque converter
clutch is hydraulically applied and is released when
fluid is vented from the hydraulic circuit by the
torque converter control (TCC) solenoid on the valve
body. The torque converter clutch is controlled by the
Powertrain Control Module (PCM). The torque con-
verter clutch engages in third gear when the vehicle
is cruising on a level plane after the vehicle has
warmed up. The torque converter clutch will disen-
gage momentarily when an increase in engine load is
sensed by the PCM, such as when the vehicle begins
to go uphill or the throttle pressure is increased. The
torque converter clutch feature increases fuel econ-
omy and reduces the transmission fluid temperature.

Fig. 2 Transmission Part Number And Serial

Number Location

1 – PART NUMBER
2 – BUILD DATE
3 – SERIAL NUMBER

AUTOMATIC TRANSMISSION—30RH

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DESCRIPTION AND OPERATION (Continued)

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