TM 55-1930-203-10
transmission, and between the transmission and miter box. They are special Sphereflex couplings, which essentially consist of gear
toothed hubs mating with an internal gear. A small amount of play is permitted between the hubs and the internal gears. This play
allows the coupling to flex as it rotates and prevents excessive stresses from occurring in either the torque converter or the
transmission.
(3) Transmission. The transmission, in conjunction with the torque converter, is used to provide three forward speeds and one
reverse with automatically varying torque ratios in each speed. In an emergency, the transmission can be shifted quickly at full power
and wide open throttle without damage to the unit.
(a) The transmission uses a compound planetary gear train in constant mesh. Four multiple disc, oil-cooled friction
clutches which are hydraulically applied and spring released, control the planetary gear train. The friction plates are steel with
sintered bronze facings the reaction plates are plain steel. A range selector valve hydraulically applies the clutches.
(b) The transmission hydraulic system is connected with the converter hydraulic system. The transmission sump serves
as a reservoir for the system. The same oil is used to drive the converter, operate the transmission range clutches, and lubricate and
cool the components of the converter and the transmission. The converter charging pump, integral with the converter, supplies the
pressure for the functioning of the converter and transmission.
(4) Miter box. The function of the miter box is to convert horizontal rotation of the transmission output flange into vertical
rotation for the column and wheel drive. At the same time, it serves as an upper support for the column and wheel drive. A right
angle bevel gear set is used to convert the horizontal input rotation to vertical output rotation. The miter box case forms an oil sump
into which the gears dip. Sufficient oil splash is obtained for adequate gear and bearing lubrication.
(5)
Air brake.
(a) The brake assembly is of the 360segmented, shoe type, actuated by an expander tube. It consists of an aluminum
torque plate upon which the expander tube is mounted. Aluminum spacers and steel side frames are attached to each side of the
torque plate and held in position by bolts. Brake linings, mounted on aluminum shoes are inserted between torque bars bolted
between the frames. The lining assemblies are held in position by retractor springs, which also act as a positive means of exerting a
retracting force to withdraw the lining from the surface of the drum after air pressure has been released.
(b) The brake is actuated by air which enters the expander tube through a reducer inlet. The air pressure is exerted 360
around the expander tube, forcing the shoe and lining assemblies, which are bearing against the tube, to move radially against the
inside diameter of the brake drum.
(c) The aluminum torque plate, which supports the brake actuating components (i.e., shoes, expander tube, and
springs), is rigidly bolted to the mounting surface of the miter box The brake drum is bolted to the miter box shaft. Two brake
assemblies are used per miter box.
(6) Column and wheel drive. The column and wheel drive assembly transmits the output torque of the miter box to the wheels.
The vertical output rotation from the miter box is converted to horizontal rotation in the wheel drive by a bevel pinion and gear. The
bevel gear is splined to the axle, which drives a spur gear in the planetary reduction gearing. The spur gear drives planet gears,
attached to the wheel. The column and wheel drive assembly swivels to facilitate steering; thereby serving as a link in the steering
system between the wheel and steering cylinders. An air tube runs through the center of the wheel axle to provide air for tire inflation.
b. Maintenance. Operator personnel are not authorized to perform maintenance on the land drive components or system. Report
all defects to organizational maintenance.
3-11. Diesel Engine
a. Description.
(1) The LARC utilizes four diesel engines (fig. 3-17) to supply power for operating the land and marine drive systems. In
addition, the engines are the power source for the electrical, hydraulic, and compressed air systems. Two engines are located in
each of the wing machinery spaces. Each engine can be started, run, and stopped independently of the others. While running, the
engine speeds can be controlled separately, or together, by the control valves in the cab. The forward starboard and aft port engines
are identical, Model No. 6080. The aft starboard and forward port engines are also identical, Model No. 6081. Fundamentally, both
model engines are the same and differ only because their location on the LARC requires that accessories be located on different
sides. On the Model 6080 engines, the water and exhaust manifolds are on the right side when viewed from
3-42