7-164. CHECKING CONTROL PRESSURE
7-167. Case pressure should not be greater than
40 PSI (2.8 kglcm2). Attach adequate gauge to
7-165. The control pressure can be checked at the
either pump or motor case as shown in figure 7-11.
transmission pump as follows:
a. Remove the. threaded plugs from the two check
7-168. VACUUM CHECK
ports and install a 600 PSI (40 kg/cm2) gauge equipped
7-169. The suction filter is equipped with a vacuum
with a short hose in each port. Make sure that the
gauge which indicates flow from the tank to the
gauges are accurately calibrated.
b. Place the Direction-Throttle Control Bail in
charge pump. The maximum vacuum at the charge
neutral. Block the drive drum safely off the ground.
pump inlet should not exceed ten inches (254 mm)
c. Start the engine and set speed at approximately
of mercury at normal
1500 RPM with the transmission in neutral. Shift the
During cold start-up it is acceptable to have a
Direction-Throttle Control Bail to the forward position
higher reading. The unit should not be operated
and observe the gauge. The pressure should be 45 PSI
until hydraulic oil is at normal operating
(3.2 kg/cm2) initially, then gradually reach charge
temperature and vacuum is below 10 inches (254
pressure. Shift the Control Bail to the reverse position.
mm) of mercury.
The gauge should indicate 45 PSI (3.2 kg/cm2) initially,
then gradually reach charge pressure.
d. If the pressures in both the forward and reverse
directions is not as specified, the control valve assembly
may be dirty or defective. If the pressure is abnormal in
7-171. DISPLACEMENT CONTROL VALVE
one direction only, the associated servo piston may be
The drive drum MUST be safely
blocked off the ground. Any
movement of control valve spool
causes the unit to shift out of neutral
and the drum will turn. Caution
personnel to stand clear of the drive