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Chevrolet Silverado / GMC Sierra. Manual - part 2905
scan tool.
The two/four wheel drive actuator assembly also has a built in incremental sensor. This device is
a linear encoder. The transfer case shift control module sends a 5 volt reference signal to the
encoder. The transfer case shift control module reads the voltage back based on the exact position
of the sector shaft of the transfer case. The transfer case shift control module knows if a shift has
been completed and if the shift is somewhere in between.
The encoder motor on the MP 1625/1626 does not have an internal brake like the NVG 246. The
encoder motor is not serviceable and must be replaced as an assembly.
Transfer Case Shift Control Module
Fig. 59: Transfer Case Shift Control Module
Courtesy of GENERAL MOTORS CORP.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
The transfer case shift control module has been standardized for all K trucks. The transfer case
shift control module contains the same hardware, boot software, and operational software found
in other GM K trucks. The only difference is the calibration file downloaded into the transfer
case shift control module memory. The transfer case shift control module comes with the
appropriate calibrations out of the factory, but new calibrations must be flashed into the transfer
case shift control module during service. This is especially important if a new transfer case shift
control module is installed during service. Calibration files may be introduced irregularly. See
your technical service bulletins.
Vehicle Speed Sensor (VSS)
There is a VSS mounted to the transfer case on the rear output shaft. The VSS is a PM generator.
The PM generator produces a AC voltage. The AC voltage and frequency increases as speed
increases. The VSS is an input to the powertrain control module (PCM). The PCM sends this
information to the transfer case shift control module via the GM LAN serial data bus.
SPECIAL TOOLS AND EQUIPMENT
SPECIAL TOOLS
Illustration
Tool Number/Description
DT-48021
Seal Installer
DT-48022
Output Bushing Installer
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
DT-48209
Bushing Remover
DT-48211
Drive Sprocket Bearing Installer
DT-48212
Input Shaft Pilot Bearing Installer
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Transfer Case - MP 1625/1626-NQF - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
