Horsepower requirements of an engine may vary continually due to the fluctuating loads; therefore, some means must be
provided to control the amount of fuel required to hold the engine speed reasonably constant during such load
fluctuations. To accomplish this control, one of three types of governors is used on the engines. Installations requiring
maximum and minimum speed control, together with manually controlled intermediate speeds, ordinarily use a limiting
speed mechanical governor. Applications requiring a near constant engine speed under varying load conditions, that
may be changed by the operator, are equipped with a variable speed mechanical governor. The hydraulic governor is
used where uniform engine speed is required under varying load conditions with a minimum speed droop.
The mechanical governors are lubricated by oil splash from the engine gear train. Oil entering the governor is directed
by the revolving governor weights to the various moving parts requiring lubrication.
The hydraulic governor is lubricated by oil under pressure from the engine.
Governor difficulties are usually indicated by speed variations of the engine. However, speed fluctuations are not
necessarily caused by the governor and, therefore, when improper speed variations become evident, the unit should be
checked for excessive load, misfiring or bind in the governor operating linkage. If none of these conditions are
contributing to faulty governor operation, contact an authorized Detroit Diesel Allison Service Outlet.
POWER TAKE-OFF ASSEMBLIES
The front and rear power take-off units are basically similar in design, varying in clutch size to meet the requirements of a
particular application. The power take-off unit is attached to either an adaptor (front power take-off) or the engine
flywheel housing (rear power take-off).
These instructions refer to field adjustment for clutch facing wear. Frequency of adjustment depends upon the amount
and nature of the load. To ensure a long clutch facing life and the best performance, the clutch should be adjusted
before slippage occurs.
When the clutch is properly adjusted, a heavy pressure is required at the outer end of the hand lever to move the
throwout linkage to the "over center" or locked position.
Adjust the clutch as follows:
1. Disengage the clutch with the hand lever.
2. Remove the inspection hole cover to expose the clutch adjusting ring. Rotate the clutch, if necessary, to bring the
adjusting ring lock within reach.
3. Remove the clutch adjusting ring spring lock screw and lock from the inner clutch pressure plate and adjusting ring.
Then, while holding the clutch drive shaft to prevent the clutch from turning, turn the clutch adjusting ring
counterclockwise as shown in Figure 10 and tighten the clutch until the desired pressure on the outer end of the hand
lever, or at the
Figure 10. Adjusting Clutch