TM 5-3895-359-14&P
will turn at crankshaft speed. However, as the blower
Gear train noise is usually an indication of excessive
drive gear has only about half as many teeth as the
gear lash, scoring, pitting or excessive bearing wear.
camshaft or balance shaft gear, it turns at approximately
Therefore, when noise develops in a gear train, the
twice the speed of the crankshaft.
flywheel housing should be removed and the gear train
and its bearings inspected. .A rattling noise usually
indicates excessive gear lash whereas a whining noise
is a result of too little gear lash.
Lubrication
Excessive wear and scoring may result from abrasive
The gear train is lubricated by overflow oil from the ,
substances or foreign material in the oil, introduced in
camshaft and balance shaft pockets spilling into the
the engine by such means as removal of the valve
gear train compartment. A certain amount of oil also
rocker cover without first cleaning away the dirt.
spills into the gear train compartment from the camshaft
and balance shaft end bearings and the idler gear
The backlash between the various mating gears in the
bearing. The blower drive gear bearing is lubricated
current 19 helix steel gear train is from .003 " to .008 "
through an external pipe leading from the main cylinder
with new parts and .010 " with used parts.
block oil gallery to the gear hub bearing support. The
idler gear bearing is pressure lubricated by oil passages
Since the camshaft and balance shaft gears each have
in the idler gear hub which connect to the oil gallery in
the same number of teeth as the crankshaft gear, they
the cylinder block.
ENGINE TIMING
1. Clean and remove the valve rocker cover.
The correct relationship between the crankshaft and
camshaft must be maintained to properly control fuel
injection, the opening and closing of the exhaust valves
2. Select any cylinder for the timing check -- it is
and engine balance.
suggested that a cylinder adjacent to one of the valve
rocker cover bolt or stud holes be chosen since the stud
or bolt may be used to mount a dial indicator.
The crankshaft timing gear can be mounted in only one
position since one attaching bolt hole is offset. The
camshaft gear can also be mounted in only one position
3. Remove the injector as outlined on Page 10-3-6.
due to the location of the keyway relative to the cams.
Therefore, when the engine is properly timed, the timing
marks on the various gears will match as shown in Fig.
An engine which is out of time may result in pre-ignition,
uneven running and a loss of power.
When an engine is suspected of being out of time due to
an improperly assembled gear train, a quick check can
be made without having to remove the flywheel and
flywheel housing by following the procedure outlined
below.
Check Engine Timing
Access to the vibration damper or crankshaft pulley, to
mark the top-dead-center position of the selected piston,
and to the front end of the crankshaft or flywheel for
turning the crankshaft is necessary when performing the
timing check. Then proceed as follows:
Fig. 2. Pointer Installation for Marking Top-Dead-
Center
10-2-104
