Dodge RAM 1500 1998 Owner's Manual page 1837

21 - 134 AUTOMATIC TRANSMISSION - 48RE
AUTOMATIC TRANSMISSION - 48RE (Continued)
1 - TORQUE CONVERTER
2 - INPUT SHAFT
3 - OIL PUMP
4 - FRONT BAND
5 - FRONT CLUTCH
6 - REAR CLUTCH
7 - PLANETARIES
8 - REAR BAND
9 - OVERRUNNING CLUTCH
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.
Fig. 2 Transmission Part Number And Serial
Number Location
1 - PART NUMBER
2 - BUILD DATE
3 - SERIAL NUMBER
GEAR RATIOS
The 48RE gear ratios are:
1st . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.45:1
2nd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.45:1
3rd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.00:1
4th . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.69:1
Rev. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.20:1
10 - OVERDRIVE CLUTCH
11 - DIRECT CLUTCH
12 - PLANETARY GEAR
13 - INTERMEDIATE SHAFT
14 - OVERDRIVE OVERRUNNING CLUTCH
15 - DIRECT CLUTCH SPRING
16 - OVERDRIVE PISTON RETAINER
17 - OIL PAN
18 - VALVE BODY
OPERATION
The application of each driving or holding compo-
nent is controlled by the valve body based upon the
manual lever position, throttle pressure, and gover-
nor 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 fourth
gear are obtained by selectively applying and releas-
ing the different clutches and bands. Engine power is
thereby routed to the various planetary gear assem-
blies which combine with the overrunning clutch
assemblies to generate 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 con-
trolled by the Powertrain Control Module (PCM). The
torque converter clutch engages in fourth gear, and
in third gear under various conditions, such as when
the O/D switch is OFF, when the vehicle is cruising
on a level surface after the vehicle has warmed up.
The torque converter clutch can also be engaged in
the MANUAL SECOND gear position if high trans-
mission temperatures are sensed by the PCM. The
torque converter clutch will disengage 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 con-
verter clutch feature increases fuel economy and
reduces the transmission fluid temperature.
Since the overdrive clutch is applied in fourth gear
only and the direct clutch is applied in all ranges
except fourth gear, the transmission operation for
park, neutral, and first through third gear will be
described first. Once these powerflows are described,
the third to fourth shift sequence will be described.
DR