DESCRIPTION
The NV144 is an electronically controlled, single-speed, AWD transfer case.
The geartrain is mounted in two aluminum case halves attached with bolts.
IDENTIFICATION
A circular ID tag is attached to the rear case of each transfer case. The ID tag provides the transfer case model number, assembly number, and serial number.
The transfer case serial number also represents the date of build.
OPERATION
The input gear is splined to the transmission output shaft. The input gear drives the mainshaft through the differential assembly. The front output shaft is operated by a drive chain that connects the shaft to a drive sprocket on the mainshaft.
The transfer case mode sensor (2) provides the Front Control Module (FCM) 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 for both the NV144 and the NV244 GENII. The operating envelope or sector rotation is -5 to 180 degrees for the NV144 and -40 to 20 degrees for the NV244 GENII. The FCM must supply 5VDC (+/- 0.5v) to the sensor whenever the FCM is not in sleep mode and monitor 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.
Scheme 77
During normal vehicle operation, the Front Control Module (FCM) monitors the mode sensor outputs at least every 2 milliseconds when the shift motor is stationary or active.
Refer to SHAFT ANGLE vs. TRANSFER CASE POSITION for the relative angles of the transfer case shift sector versus the interpreted transfer case gear operating mode.
The selector switch assembly is mounted in the right side of the vehicle's Instrument Panel (IP) and consists of a rotary knob connected to a resistive network for the mode shift selections.
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 Front Control Module (FCM) are provided that interpret the selector switch resistance as given in the SELECTOR SWITCH INTERPRETATION table.
The shift motor (1) is an electromechanical device consisting of a DC permanent magnet motor, a motor brake, a gear train and an analog position sensor. The shift motors overall function is to move and lock a gear that moves the mode fork found in the transfer case. This allows the transfer case to be shifted electrically to multiple operating positions (4LOCK and AWD). The operating current of the shift motor under stall conditions is 30 amps maximum at 72°F with 13.5 volts, at the motor leads.
Scheme 78
Shifting in the transfer case occurs when the shift motor brake is released and a Pulse Width Modulated (PWM) voltage is supplied to the shift motor by the Front Control Module (FCM). A linear analog position sensor located inside the shift motor, provides the FCM with the motors angular, rotational position. With this information, the FCM 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.