THEORY OF OPERATION
This section describes how major systems and components of the carrier operate. An understanding of how each part
functions in a system and how components relate to each other will help solve possible maintenance problems with the carrier.
INTEGRATED SYSTEMS AND COMPONENTS
The M548A1 power plant consists of the diesel engine, transfer gearcase, and transmission. The M548A3 power plant
consists of the diesel engine and hydromechanical cross drive transmission. The fuel, exhaust, cooling, starter, generator, and
engine air systems are support systems are support systems for the power plant.
Engine power is supplied by a liquid cooled, 6cylinder, V-type, compression ignition (diesel) unit. Starting is by a heavy
duty 24 V starter. Engine is protected from low oil pressures and high temperatures by transmitters in the oil and cooling
systems which activate warning light circuits.
The M548A1 transfer gearcase transfers power from the engine flywheel to the transmission torque converter through four
gears at a ratio of 1 to 1.286. An engine disconnect allows the engine to operate independently of the rest of the power plant.
A power takeoff within the transfer gearcase drives the cooling fan through a pulley and drive belts. Another power takeoff
within the transfer gearcase drives the 100 amp generator through a pulley and drive belts. A third power takeoff within the
transfer gearcase drives the winch.
The M548A1 transmission is a three speed, constant mesh, planetary gear train with hydraulic torque converter and lockup
clutch. It automatically selects the proper gear based on road and load conditions and range selected. The transmission
delivers power from the transfer gearcase to the differential.
The M548A3 diesel engine delivers power directly to a hydromechanical cross drive transmission with hydrostatic steering.
This transmission delivers power from the engine to the left and right final drives through the propeller shafts. The final drives
power the drive sprockets in the suspension system. This transmission has its own oil system with filters and separately
mounted engine and transmission oil cooler. The transmission oil system is separate from the engine oil system. The 200 amp
generator and cooling fan are engine driven with drive belts and pulleys.