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 257 of 481

TM 9-2320-272-10

2-156

Change 2

2-26. OPERATION OF TRACTOR AND FIFTH WHEEL (Contd)

d.

Uncoupling Semitrailer.

.

WARNING

.

Use ground guide when backing up

to park semitrailer. Failure to do

this will result in damage to

vehicle, injury, or death.

(1)

Push trailer air supply valve

(M931/A1/A2 and M932/A1/A2 (1) in.

(2)

Place semitrailer in proper

location and engage airbrake hand control

lever/Johnnie bar (2) and parking brake

lever (3).

(3)

Place wheel chocks (12) in front

and behind semitrailer wheels.

(4)

Place landing gear float pads (6)

on ground under semitrailer landing gear (5).

(5)

Turn crank (4) until landing

gear (5) makes firm contact with float pads (6).

CAUTION

Ensure all lights are turned to

OFF position. Failure to do this

will result in damage to vehicles

electrical system.

(6)

Disconnect and remove electrical

cable (8) from semitrailer and secure cable (8)

on tractor.

(7)

To release semitrailer kingpin

(11), pull plunger handle (14) forward, then

out, to open fifth wheel coupling jaws (13).

.

WARNING

.

Do not pull tractor forward beyond

approach ramps until all air lines

are disconnected. Failure to do this

will result in injury or death.

(8)

Move tractor forward until fifth wheel (9) is clear of semitrailer.

(9)

Turn handle (16) of airbrake hose shutoff valve (15) to the closed position.

(10)

Disconnect airhose couplings (7) from semitrailer and secure airhose

couplings (7) on tractor.

(11)

Disengage airbrake hand control lever/Johnnie bar (2) and parking

brake lever (3), and continue operations without trailer.