DETROIT DIESEL 53
1.7.3
CAMSHAFT AND BALANCE SHAFT GEARS
The camshaft and balance shaft gears on an In-line engine are located at the flywheel end of the engine and
mesh with each other and run at the same speed as the crankshaft.
Since the camshaft and balance shaft gears on In-line engines must be in time with each other, timing marks
are stamped on the rim of each gear. Also, since these two gears as a unit must be in time with the crankshaft,
timing marks are located on the idler and crankshaft gears (refer to Section 1.7.1).
Each gear is keyed to its respective shaft 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 on some engines. The retainer is
attached to the gear by bolts threaded into tapped holes in the gear. On the three cylinder In-line engines,
external weights are attached to the rear face of each gear. The weights are important in maintaining perfect
engine balance.
When new service gears are used on an In-line engine, the external weights on the old gears must be
'transferred to the new gears. If the weights are transferred to new gears, tighten the bolts to 45-50 lb-ft torque.
Remove Camshaft and Balance Shaft Gears
1. Remove the camshaft and the balance shaft from the engine as outlined in Section 1.7.2.
2. Place the camshaft and gear assembly in an arbor press with the gear suitably supported as shown in Fig.
1.
3. Place a wood block under the lower end of the camshaft so the threads will not be damaged when the shaft
is pressed from the gear.
4. Place a short piece of 3/4" O.D. brass rod between the end of the camshaft and the ram of the press; then
force the camshaft out of the camshaft gear.
5. Remove the thrust washer, Woodruff key and spacer from the camshaft.
6. Remove the gear from the balance shaft in a similar manner.
Figure 1. Removing Camshaft Gear
Inspection
Clean the gears with fuel oil and dry them with compressed air. Then examine the gear teeth for evidence of
scoring, pitting and wear. Replace the gears if necessary.
Examine both faces of the camshaft and balance shaft thrust washer and, if either face is worn or scored,
replace the washer. Also examine the surface on the camshaft and balance shaft which the thrust washer
contacts. If this surface is scratched, but not severely scored, smooth it up with a fine oil stone.
Install Camshaft and Balance Shaft Gears
1. Note the letters stamped on the end of the camshaft which signify the engine models in which a camshaft
may be used. The letters on the timing gear end of the camshaft must correspond with the engine model of the
particular engine being assembled. Refer to the front of this manual for engine model identification.
2. Place the rear camshaft spacer over the timing gear end of the camshaft and install the Woodruff key.
3. Lubricate the thrust washer with clean engine oil and place the thrust washer over the gear end of the
camshaft and the spacer.
July, 1970 SEC. 1.7.3 Page 1
