Chevrolet Silverado / GMC Sierra. Manual — part 2953
Fig. 58: Transfer Case I.D. Label
Courtesy of GENERAL MOTORS CORP.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Fig. 59: Magna Transfer Case Bar Code Label
Courtesy of GENERAL MOTORS CORP.
TRANSFER CASE DESCRIPTION AND OPERATION
The Magna Powertrain (MP) model 3023/3024 RPO NQH transfer case is a 2 speed automatic,
active transfer case (ATC). The MP 3023/3024 ATC provides 5 modes, Auto 4WD, 4HI, 4LO,
2HI and NEUTRAL. The Auto 4WD position allows the capability of an active transfer case,
which provides the benefits of on-demand torque biasing wet clutch and easy vehicle tuning
through software calibrations. The software calibrations allow more features such as flexible
adapt ready position and clutch preload torque levels. The technology allows for vehicle speed
dependent clutch torque levels to enhance the performance of the system. For example, the system
is calibrated to provide 0-6.78 N.m (0-5 lb ft) of clutch torque during low speed, low engine
torque operation, and predetermined higher torque for 40 km/h (25 mph) and greater. This
prevents crow-hop and binding at low speeds and provides higher torque biases at higher vehicle
speeds, in order to enhance stability.
Transfer Case Shift Control Switch
Callout
Component Name
1
Component Identifier
2
GM Broadcast Code
3
Supplier Code
4
Production Year
5
Julian Date of the Year
6
Assembly Line Number
7
Sequential Number
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Fig. 60: Transfer Case Shift Control Switch
Courtesy of GENERAL MOTORS CORP.
The MP 3023/3024 ATC transfer case features a 4 mode shift control switch located on the
instrument panel. When the ignition key is in the RUN position, the transfer case shift control
module monitors the transfer case shift control switch to determine if the driver desires a new
mode/range position. At a single press of the transfer case shift control switch, the lamp of the
new desired position will begin flashing to inform the driver that the transfer case shift control
module has received the request for a new mode/range position. The lamp continues to flash until
all shifting criteria has been met and the new mode/range position has been reached, or has been
engaged. Once the new mode/range position is fully active, the switch indicator lamp for the new
position will remain ON constantly.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
During normal driving situations, the transfer case can operate in the Auto 4WD mode. In the
Auto 4WD mode, the transfer case shift control module monitors rear wheel slip speed, based on
the inputs from the wheel speed sensors. When the vehicle experiences a rear wheel slip
condition, the transfer case shift control module sends a pulse width modulated (PWM) signal to
an electronic motor, which is the transfer case 2/4 wheel drive actuator assembly. This actuator
rotates the transfer case control actuator shaft, applying a clutch. The clutch is designed to deliver
a variable amount of torque, normally delivered to the rear wheels, and transfers it to the front
wheels. Torque is ramped up to the front wheels until the front wheel speed sensors matches that
of the rear speed sensors. Torque is ramped down to the front wheels. The process would repeat if
rear wheel slip is detected again.
The MP 3023/3024 ATC transfer case has the added feature of also providing the driver with 4
manual mode/range positions:
4HI - 4 Wheel Drive high range
2HI - 2 Wheel Drive high range
4LO - 4 Wheel Drive low range, 2.68:1 gear ratio reduction
Neutral
The driver may choose to select any of these mode/range positions while driving the vehicle.
However, the transfer case will not allow a shift into or out of 4LO unless the following criteria
has been met:
The ignition switch is in RUN.
The automatic transmission is in PARK or NEUTRAL.
The vehicle speed is below 5 km/h (3 mph).
This transfer case also has a NEUTRAL position. A shift to the NEUTRAL position allows the
vehicle to be towed without rotating the transmission output shaft. In the NEUTRAL position, the
rear propeller shaft rotates the transfer case rear output shaft, in turn rotating the oil pump, thus
providing constant lubrication during towing. NEUTRAL position may be obtained only if the
following criteria has been met:
The ignition switch is in RUN.
The automatic transmission is in PARK or NEUTRAL.
The vehicle speed is below 5 km/h (3 mph).
The transfer case is in 2HI mode.
Once these conditions have been met, press and hold both the 2HI and 4LO buttons for 10
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 3023/3024-NQH - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
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