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TM 55-1905-221-14-3
The camshaft and balance shaft gears, located at the flywheel end of the engine, mesh with each other and run at
the same speed as the crankshaft. Either one of the gears may be driven from the crankshaft timing gear, through an
idler gear, depending upon engine rotation. Viewing the engine from the flywheel or gear train end, the right-hand gear,
whether on the balance shaft (LD, RD engines) or camshaft (LB, RB engines), has left-hand helical teeth, and the
left-hand gear has right-hand helical teeth. The idler gear mates with the left-hand gear on right-hand rotation engines,
and with the right-hand gear on left-hand rotation engines.
Since the camshaft and balance shaft gears must be in time with each other, the letter "O" is stamped on one tooth
of one of the gears with a corresponding mark at the root of the mating tooth of the other gear. Also, since these two
gears as a unit must be in time with the crankshaft, identification marks (letter "R" or "L" for right-hand or left-hand
rotation engines, respectively) are located on either the camshaft gear or balance shaft gear and the mating idler gear
The camshaft and balance shaft gears are keyed to their respective shafts and held securely against the shoulder on
the shaft by a nut. A gear nut retainer, with a double hexagon hole in the center, fits over the nut and prevents loosening
of the nut. The retainer is attached to the gear by bolts threaded into tapped holes in the gear. These tapped holes are
also utilized in mounting an accessory drive on the camshaft or balance shaft gear. The same two gears are used as
camshaft and balance shaft gears. A small balance weight is attached to the inner face of each gear. A different size
weight is secured with two 3/8"-24 X 1--1/4" bolts. These weights are important in maintaining perfect engine balance.


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