TM 5-3810-300-24&P-3
1.7.3
CAMSHAFT AND BALANCE SHAFT GEARS
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 (Fig. 1). Viewing
the engine from the flywheel or gear train end, the right-
hand gear, whether on the balance shaft (RA and RD
engines) or camshaft (RB and RC 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.
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, an identification mark (letter "R" for right-
hand rotation) is located on either the camshaft gear or
Fig. 1 - Camshaft and Balance Shaft Gear Mounting
balance shaft gear and the mating idler gear (see Fig. 1
16.
Gear--Idler
33.
Gear--R.H. Helix-
18.
Gear--L.H. Helix-
Balance Shaft
Camshaft
The camshaft and balance shaft gears are keyed to their
respective shafts and held securely against the shoulder
5. Turn puller screw down against end of shaft to
on the shaft by a nut. A gear nut retainer, with a double
remove gear.
hexagon hole in the center, fits over the nut and prevents
loosening of the nut. The retainer is attached to the gear
6. Remove gear from balance shaft in similar manner.
by bolts threaded into tapped holes in the gear. These
tapped holes are also utilized in mounting an accessory
7. If necessary, remove two weight retaining bolts and
drive on the camshaft or balance shaft gear.
remove balance weights from each gear.
The same two gears are used as camshaft and balance
shaft gears on three, four and six cylinder engines. A
8. If necessary, remove keys from camshaft and
small balance weight is attached to the inner face of
balance shaft.
each gear. A different size weight is used on three, four
and six cylinder engines. The three cylinder engine
Inspection
weight is secured to the gear with two 3/8"-24 x 1-1/8"
bolts, the four cylinder engine weight is secured with two
Clean the gears with fuel oil and dry them with
3/8"-24 x 1-3/8" bolts and the six cylinder engine weight
compressed air. Then examine the gear teeth for
is secured with two 3/8"-24 x 1-1/4" bolts. These weights
evidence of scoring, pitting, wear or burning. If severely
are important in maintaining perfect engine balance.
damaged or worn, install a new gear. Also check the
other gears in the gear train.
Remove Camshaft and Balance Shaft Gears
Install Camshaft and Balance Shaft Gears
1. Remove camshaft and balance shaft from engine as
outlined in Section 1.7.
1. Install the balance weights on the gears, if removed.
2. Support the camshaft suitably in soft jaws of bench
2. Lubricate the shaft journals and place the cam-shaft
vise, being careful not to damage cams.
and balance shaft end bearings in place, with the
bolting flanges facing toward the gear ends of the
3. Remove nut retaining gear on camshaft.
shafts. If the unit being serviced is an "A" or "D"
4. Back out puller screw of tool J 1902-01 and attach
engine, install the thrust
puller to outer face of gear with four bolts (Fig. 2).
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