MP3023 Transfer Case - Service Information: Overview Dodge Durango III

DESCRIPTION

The Select-Trac® II is the MP3023 two-speed, on-demand, active four-wheel drive transfer case that provides optimum traction for a wide range of conditions, while maximizing driver convenience. When operating in 4WD Auto mode, this sophisticated system anticipates and prevents slip by redirecting torque as necessary.

For added traction capability when traversing steep grades, rough terrain or extremely poor traction surfaces, the transfer case includes a 4WD Low mode. This second speed gear multiplies engine torque 2.72 times and locks the clutch pack for maximum traction.

Electric shifting between 4WD AUTO and 4WD Low is effected with a console-mounted switch. A pushpin button is used to shift to Neutral mode.

The MP3023 transfer case provides the following benefits

1. Active, on-demand four-wheel drive requires no driver input.
2. Instantly anticipates slip and preemptively redirects torque as needed.
3. Vehicle stability under all conditions because torque is constantly being transferred.
4. 4WD Low operation mode provides an advantage over vehicles equipped with a single-speed all-wheel drive transfer case.
5. Electric shifting between 4WD Auto and 4WD Low provides smooth operation and improved NVH control compared to systems with mechanical linkage.
6. Enhanced traction and stability provided by the Traction Control and Electronic Stability Program (ESP) working in tandem with four-wheel-drive.
7. A robust design and sealing for reliability.
8. Maintenance-free.
9. A neutral mode permits flat towing.

OPERATION

Shifting in the transfer case occurs when a Pulse Width Modulated (PWM) voltage is supplied to the shift motor (3) by the Drive Train Control Module (DTCM). A linear analog position sensor (Encoder) (2) located on the rear transfer case housing, provides the DTCM with the motors' angular, rotational position. With this information, the DTCM continuously knows the motors' position, and therefore allows it to accurately control the motors' operation, including voltage polarity which is used to control motor direction.

The electronically controlled wet clutch pack uses an electric motor to actuate an internal gear train, clutch cam, and low range barrel cam. The clutch cam actuates the clutch levers that apply normal force to the multi-disc wet clutch pack. The clutch disks are alternately splined to the front and rear outputs. When normal force is applied to this clutch pack, torque is transferred to equalize speed differences between front and rear axles.

The transfer case Encoder (2) provides the Drive Train Control Module (DTCM) feedback about the position of the transfer case. The sensor consists of a linear analog position sensor that converts the motor output shaft position into a DC signal. The sensor may rotate a full 360 degrees. The DTCM must supply 5VDC (+/- 0.5v) to the sensor whenever the DTCM is not in sleep mode and monitors the shift motor position. The sensor position is monitored when the ignition is in the RUN position and for 10 seconds after the ignition is shifted to the OFF position. The sensor is mechanically linked to the shaft of the cam which allows the transfer case to shift. The mode sensor will draw less than 20 mA of current during operation.

During normal vehicle operation, the DTCM monitors the mode sensor outputs at least every 2 milliseconds when the shift motor is stationary or active. The mode sensor position will be considered invalid by the DTCM if the voltage is greater than 4.75 V or if it is less than 0.25 V.

Note. All the parameter voltages referred to in the following information are calibrated items in the controller software and are subject to change.

The DTCM shall consider Transfer Case position based on the MODE SENSOR VOLTAGES table listed below

MODE SENSOR VOLTAGES