DETROIT DIESEL 53
Gear Train and Timing 1.7.1
The crankshaft gear is stamped "VR-A" on the left side
of a triangle timing mark (Fig. 1)for a right-hand rotation
For advance timing, the "A" adjacent to the "VR" on the
crankshaft gear is aligned with the circle-triangle on the
There are no timing marks on the governor drive gear
blower rotor gears, blower drive gear or the accessory
drive (fuel pump) gear. Therefore, it is not necessary to
align these gears in any particular position when
meshing the various gears with the camshaft gears.
Gear train noise is usually an indication of excessive
gear lash, chipped, pitted or burred gear teeth or
excessive bearing wear; therefore, when noise develops
in a gear train, remove the flywheel housing and inspect
the gear train and its bearings. A rattling noise usually
indicates excessive gear lash whereas a whining noise
indicates too little gear lash.
The camshaft gears are positioned so that the triangle
The backlash between the various mating-gears in the
timing marks are adjacent to each other (Fig. 2). One
gear train should he .003" to .005", except the blower
circle-triangle timing mark on the idler gear is aligned
rotor gears which should be .0005" to .0025". Maximum
with the second "triangle" on the mating camshaft gear.
permissible backlash between worn blower gears is
The other timing mark on the idler gear is aligned with
.0035", and should not exceed .007" clearance between
the proper timing mark on the crankshaft gear.
all other gears in the gear train.
1972 General Motors Corp.
SEC. 1.7.1 Page 3