TM-9-2320-285-24-1
TRUCK TRACTOR, YARD TYPE, 43,500 LB GVW, DED, 4X2, ARMY MODEL M878A1
TECHNICAL MANUAL; ORGANIZATIONAL, DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE MANUAL
OCTOBER 1985
TM-9-2320-285-24-1 - Page 14 of 987
TM 9-2320-285-24-1
Section III.
PRINCIPLES OF OPERATION
Para
Yard Tractor .
.................................................
1-15
Engine .
..........................................................
1-16
Fuel System.
..................................................
1-17
Exhaust System.
............................................
1-18
Cooling System .
............................................
1-19
Electrical System.
..........................................
1-20
Transmission and Propeller
Shaft.
..........................................................
1-21
Axles.
.............................................................
1-22
Para
Brakes.
...........................................................
1-23
Wheels .
..........................................................
1-24
Steering System.
............................................
1-25
Frame and Towing Attachments .
...................
1-26
Springs and Shock Absorbers .
......................
1-27
Cab and Body.
................................................
1-28
Accessories.
...................................................
1-29
Fifth Wheel Hydraulic System.
.......................
1-30
Cab Tilt Hydraulic System.
.............................
1-31
Gages.
............................................................
1-32
1-15.
YARD TRACTOR
1.
ENGINE.
Diesel engine, internal combustion power unit; engine has no carburetor or electrical ignition system,
relies on heat of compressed air alone to ignite fuel; heat of diesel fuel is converted to work in engine cylinders.
2.
FUEL SYSTEM.
Fuel is pumped from fuel tank into fuel injectors, then sprayed into combustion chamber.
3.
EXHAUST SYSTEM.
Engine exhaust gases are expelled through muffler and exhaust stack mounted on right
side of tractor; muffler aids in quieting engine noise.
4.
COOLING SYSTEM.
Cools engine by circulating coolant; cooling air is drawn through radiator by belt-driven fan;
water pump draws coolant from radiator.
Radiator is equipped with coolant recovery system.
5.
ELECTRICAL SYSTEM.
12 volt, supplied by four wet-cell batteries in parallel; engine-driven, 90 ampere alternator
supplies current.
Key switch controls application of power to circuits.
6.
POWER TRAIN.
Consists of transmission, propeller shaft, differential, and rear axle; transmits motive power from
engine to rear wheels.
7.
BRAKES.
Drum type, operated by air pressure; service brakes controlled by cab brake treadle, independent of
parking brake control.
1-5
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