TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 52 of 481
TM 9-2320-272-10
1-35
1-17. CONTROL SYSTEM OPERATION (Contd)
TRANSFER CASE SHIFT LEVER SWITCH
– When depressed with
transmission in neutral, signals interlock solenoid valve to exhaust air
pressure from interlock air cylinder and actuates lock-up solenoid.
TRANSFER CASE SHIFT LEVER
– Is pushed down to high for light load
operations, and up to low for heavy load operations. Six-wheel drive is
achieved automatically when transfer case shift lever is placed in low.
TRANSFER CASE POWER TAKEOFF CONTROL LEVER
– Manual
control for engaging power takeoff.
TRANSFER CASE POWER TAKEOF
F – Mounted and mechanically driven
at rear of transfer case, the PTO drives a pump to supply hydraulic pressure
to power the rear winch and crane on the M936/A1/A2 wreckers.
FRONT-WHEEL DRIVE LOCK-IN SWITCH
– Manual control for
activating front-wheel drive valve to provide front-wheel drive with transfer
case in high drive range.
E
D
C
B
A
INTERLOCK AIR CYLINDER
– Under air pressure, a piston in the
interlock air cylinder forces a shaft against one of three grooves in transfer
case shift lever. This prevents transfer case from being shifted with
transmission in gear.
INTERLOCK SOLENOID VALVE
– Releases air from interlock air cylinder
when transmission is in neutral and transfer case shift lever switch is
depressed. This permits the transfer case high/low shift shaft to move.
FRONT-WHEEL DRIVE AIR CYLINDE
R – When under pressure, it moves
transfer case clutch forward to engage front-wheel drive.
FRONT-WHEEL DRIVE VALVE
– When tripped by transfer case shift
shaft, the front wheel drive valve routes air to front-wheel drive air cylinder.
I
H
G
F
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