Figure 3-15. Checking pump and converter pressure.

pump, clogged converter orifice in pump collector ring or

a faulty cooler by-pass valve.

(3) Clutch pressure (at stall).

(a) To check clutch pressures; install a

pressure gauge in the front port on top of the

Figure 3-16. Checking clutch pressure.

(b) Check clutch pressure in forward

ME 3930-618-34/3-15

and reverse direction by the following method. Position

truck against wall and apply both the parking and the foot

Figure 3-15. Checking pump and converter pressure.

brake-drive wheels must be locked. Accelerate engine

momentarily to wide open throttle with truck in a stalled

(b) If the pump pressure is between

condition. Note the pressure indicated on the pressure

100-psi and 140-psi, the pump is in normal operating

gauge. Engine rpm should not exceed 1500.

condition.

does not go above normal pump pressure, the pressure

check the regulator valve spring and spool; check the

in the clutch circuit is normal. Pressure should never be

cooler by-pass and check for restricted lines and

below 65-psi.

passages.

(d) If the pressure is below 65-psi,

(d) If the pump pressure is below 100-

check for low oil level, restricted lines or passages,

psi, check for low oil level, a faulty pump, excessive line

damaged collector rings, faulty or incorrectly adjusted

leakage, a faulty directional valve, or clogged inlet filter.

selector valve, faulty pump or excessive leaks in the

(2) Torque converter pressure.

clutch drum assembly. (4)

Clutch

pressure(Free

(a) To check converter pressure, install

running). To check the clutch pressure with the drive

a pressure gauge calibrated to 300-psi, in the port

wheels free running, the following instructions are to be

marked "C" on the right side of the transmission (fig. 3-

used.

15). Leave the transmission in neutral and start the

(a) Raise both drive wheels off floor and

engine. Accelerate the engine to full governed speed of

block securely with both wheels free to rotate.

2200-rpm and note the pressure indicated on the

(b) Hold inching pedal up so inching

pressure gauge.

valve plunger cannot move.

(b) If the converter pressure is 65-psi to

100-psi maximum, the converter is in normal operating

with shift lever in either forward or reverse position.

condition. With the engine idling at 500rpm, converter

Check pressure in both directions.

pressure will be 15-psi to 60-psi.

(d) If pressure is abnormal, check

2200rpm, check for cause of excessive pump pressure;

enlarged metering orifice, restricted converter return

passages, or maladjustment of cooling circuit resistor

valve.

(d) If the pressure is below 65-psi,

check for low oil level, restricted intake screen, faulty

3-21