TM-9-2320-272-23-1

TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)

TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5

SEPTEMBER 2012

TM-9-2320-272-23-1 - Page 1156 of 1313

FIELD MAINTENANCE

FRONT WHEEL DRIVE DOES NOT ENGAGE (FRONT WHEEL DRIVE LOCK-IN SWITCH ENGAGED AND

TRANSFER CASE SHIFT LEVER IN HIGH POSITION)

INITIAL SETUP:

Tools and Special Tools

Tool Kit, General Mechanic's: Automotive

(Volume 5, WP

0826, Table 1, Item 56)

Gauge, Pressure

(Volume 5, WP

0826, Table 1, Item 19)

Test Set, Electronic Systems

(Volume 5, WP

0826, Table 1, Item 51)

Personnel Required

(2)

References

Point to Point Schematics

References (cont.)

WP

0131

Volume 3, WP

0389

Volume 5, WP

0805

Equipment Condition

Vehicle parked and engine shut down.

(TM

9-2320-272-10)

TROUBLESHOOTING PROCEDURE

FRONT WHEEL DRIVE DOES NOT ENGAGE (FRONT WHEEL DRIVE LOCK-IN SWITCH ENGAGED AND

TRANSFER CASE SHIFT LEVER IN HIGH POSITION)

NOTE

Conduct these malfunction tests if front wheel drive does not engage. This procedure will

check for leaking air lines from the actuator valve to transfer case and the supply line from

the actuator valve to transfer case. It also checks for faulty actuator valve, front wheel drive

lock-in switch, and air line from actuator valve to front wheel drive lock-in switch. Finally, it

checks for transfer case not engaging front wheel drive, and air not being delivered to the

actuator valve.

TM 9-2320-272-23-1

0140

0140-1