Dodge Ram Truck 1500-2500-3500. Manual — part 1892

SEAL-FRONT OUTPUT SHAFT

REMOVAL

1. Remove the front propeller shaft (Refer to 3 - DIF-

FERENTIAL & DRIVELINE/PROPELLER SHAFT/
PROPELLER SHAFT - REMOVAL).

2. Remove the front propeller shaft seal boot retaining

clamp (2).

3. Remove the front propeller shaft seal boot (1) from

the front output shaft seal slinger.

4. Remove the front output shaft seal slinger (1) by

bending the slinger away (2) from the transfer
case.

5. Using a suitable pry tool, remove the slinger from

the output shaft using care not to damage the
shaft.

6. Using a screw and a slide hammer, remove the

front output shaft seal.

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INSTALLATION

1. Install the new front output shaft seal with Installer MB991168A.

2. Install the front output shaft seal slinger with Installer 8840. Install the slinger onto the shaft until the tool contacts

the rear of the output shaft.

3. Install a new seal boot clamp onto the seal boot.

4. Install the seal boot and clamp onto the slinger hub and tighten the clamp with Crimp Tool C-4975-A.

5. Install front propeller shaft (Refer to 3 - DIFFERENTIAL & DRIVELINE/PROPELLER SHAFT/PROPELLER

SHAFT - INSTALLATION).

SENSOR-MODE

DESCRIPTION

The transfer case mode sensor is an electronic device whose output can be interpreted to indicate the shift motor
shaft’s rotary position. The sensor consists of a magnetic ring and four Hall Effect Transistors to create a 4 channel
digital device (non-contacting) whose output converts the motor shaft position into a coded signal. The TCCM must
supply 5VDC (+/- 0.5v) to the sensor and monitor the shift motor position. The four channels are denoted A, B, C,
and D. The sensor is mechanically linked to the shaft of the cam which causes the transfer case shifting. The mode
sensor draws less than 53 mA.

OPERATION

During normal vehicle operation, the Transfer Case
Control Module (TCCM) monitors the mode sensor
outputs at least every 250 (+/-50) milliseconds when
the shift motor is stationary and 400 microseconds
when the shift motor is active. A mode sensor signal
between 3.8 Volts and 0.8 Volts is considered to be
undefined.

Refer to SECTOR ANGLES vs. TRANSFER CASE
POSITION for the relative angles of the transfer case
shift sector versus the interpreted transfer case gear
operating mode. Refer to MODE SENSOR CHANNEL
STATES for the sensor codes returned to the TCCM
for each transfer case mode sensor position. The var-
ious between gears positions can also be referred as
the transfer case’s coarse position. These coarse positions come into play during shift attempts.

SECTOR ANGLES vs. TRANSFER CASE POSITION

Shaft Angle (Degrees)

Transfer Case Position

+40

4LO

+20

N

0

2WD/AWD

-20

4HI

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MODE SENSOR CHANNEL STATES

Transfer Case

Angle (degrees)

Sensor Channel A

Sensor Channel B

Sensor Channel C

Sensor Channel D

Between Gears

H

H

L

H

+40 (4LO)

H

H

L

L

Between Gears

H

H

L

H

Between Gears

H

L

L

H

+20 (NEUTRAL)

H

L

L

L

Between Gears

H

L

L

H

Between Gears

H

L

H

H

0 (2WD/AWD)

H

L

H

L

Between Gears

H

L

H

H

Between Gears

L

L

H

H

-20 (4HI)

L

L

H

L

Between Gears

L

L

H

H

Between Gears

L

H

H

H

SWITCH-TRANSFER CASE SELECTOR

DESCRIPTION

The selector switch assembly is mounted in the left side of the vehicle’s Instrument Panel (IP) and consists of a
rotary knob connected to a resistive network for the mode and range shift selections. Also located in this assembly
is a recessed, normally open momentary switch for making shifts into and out of transfer case NEUTRAL. A pen, or
similar instrument, is used to make a NEUTRAL shift selection, thus reducing the likelihood of an inadvertent shift
request.

The selector switch also contains light emitting diode’s (LED’s) to indicate the transfer case position and whether a
shift is in progress.

OPERATION

As the position of the selector switch varies, the resistance between the Mode Sensor supply voltage pin and the
Mode Sensor output will vary. Hardware, software, and calibrations within the Transfer Case Control Module
(TCCM) are provided that interpret the selector switch resistance as given in the table below: SELECTOR SWITCH
INTERPRETATION

SELECTOR SWITCH INTERPRETATION

Step

Resistance Range (ohms)

Required Interpretation

A

<200

Shorted

B

400-700

NEUTRAL

C

1050-1450

4LO

D

1850-2300

4H

E

3050-5950

AWD (Default)

F

9.5-12.5K

In between positions

G

>15.5K

Open

For resistances between the ranges B-E shown for each valid position (T-Case NEUTRAL, 4LO, 4HI, AWD), the
TCCM may interpret the resistance as:

•

either of the neighboring valid positions.

•

as an invalid fault position.

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For resistances between the ranges E and F shown for AWD and in-between positions, the TCCM may interpret the
resistance as:

•

the AWD position.

•

an invalid fault position.

•

a valid in-between position.

For resistances between the ranges F and G shown for in-between positions and fault condition (open), the TCCM
may interpret the resistance as:

•

a valid in-between position.

•

an invalid fault position.

For resistances between the ranges A and B shown for the fault condition (short) and , T-Case NEUTRAL, the
TCCM may interpret the resistance as:

•

the T-Case NEUTRAL position.

•

an invalid fault position.

The LED’s in the selector assembly are illuminated/flashed in the following manner to indicate a particular condition
or state.

•

A solidly illuminated LED indicates a successfully completed shift and the current operating mode of the trans-
fer case. While a shift has been requested but not yet completed, the LED for the desired transfer case posi-
tion is flashed.

•

A flashing operating mode LED for the desired gear indicates that a shift to that position has been requested,
but all of the driver controllable conditions have not been met. This is in an attempt to notify the driver that the
transmission needs to be put into NEUTRAL, the vehicle speed is too great, or some other condition outlined
(other than a diagnostic failure that would prevent this shift) elsewhere (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/TRANSFER CASE CONTROL MODULE - OPERATION) is not met. Note that
this flashing will continue indefinitely until the conditions are eventually met, or the selector switch position is
changed, or if diagnostic routines no longer allow the requested shift.

•

If the driver attempts to make a shift into transfer case NEUTRAL, and any of the driver controllable conditions
are not met, the request will be ignored until all of the conditions are met or until the NEUTRAL select button
is released. Additionally the neutral lamp will flash, or begin to flash while the button is depressed and operator
controllable conditions are not being met. All of the LED’s except the Neutral will flash if any of the operator
controllable conditions for shifting are not met while the Neutral button is depressed. This

9

toggle

9

type of fea-

ture is necessary because the TCCM would interpret another request immediately after the shift into transfer
case NEUTRAL has completed.

•

No LED’s illuminated indicate a fault in the transfer case control system.

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