SPOOL 1397761 - Caterpillar

Testing The Modulating Valves
Illustration 1 g06179468
Modulating Valves (Electronic Clutch Pressure Control)
(1) Modulating valve 5
(2) Modulating valve 4
(3) Modulating valve 1
(4) Modulating valve 2
(5) Modulating valve 3
(6) Modulating valve 6The pressure test points for the transmission clutches are installed in the modulating valves (electronic clutch pressure control). The modulating valves (electronic clutch pressure control) are located on the lower left side of the transmission.With a stationary machine, the pressure of the oil in the transmission clutches can only be tested on the valve that is engaged when the transmission is in neutral. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures".With the transmission in neutral, if the pressure in the engaged valve is correct, the oil supply to the modulating valves (electronic clutch pressure control) is sufficient.The pressures for the remaining clutches must be measured on a moving machine. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures" for the correct procedure to test the pressures in the transmission clutches.If the transmission is observed to slip in one gear, a transmission clutch may not be functioning correctly. Use Table 1 in order to determine the transmission clutch that may not be functioning correctly.
Table 1
CX38–P892 SPEED SELECTION
SPEED ENGAGED CLUTCHES
(= ENERGIZED VALVES)
First Gear Reverse 1. 4, and 5
Second Gear Reverse 1, 4, and 6
Neutral 1 1 and 4
Neutral 2 1 and 3
First Gear Forward 3, 4, and 6
Second Gear Forward 1, 3, and 4
Third Gear Forward 2, 3, and 4
Fourth Gear Forward 3, 5, and 6
Fifth Gear Forward 1, 3, and 5
Sixth Gear Forward 2, 3, and 5
Seventh Gear Forward 1, 2, and 5
Eighth Gear Forward 1, 2, and 3
Ninth Gear Forward 2, 3, and 6 Testing The Solenoid Coil Assembly
The function of the solenoids can be tested by running a calibration of the transmission. It is possible to monitor pressures in the clutches when a calibration sequence is being run. The calibration will also alert the operator to any faults that are detected with the transmission clutches.Note: The pressures that can be observed during a calibration are not the full pressures of a clutch engagement. Use a 0 to 2750 kPa (0 to 400.0 psi) gauge to measure the pressures. From the pressures that are observed, it is possible to determine if the solenoid is functioning correctly, and if the solenoid is allowing the clutches to fill with oil.Run a calibration of the planetary transmission and observe the pressures of the oil in the clutches. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures" and Systems Operation, Testing and Adjusting, "Transmission - Calibrate".Observe the pressure for each clutch. If a pressure rise is noted, the solenoid and the related electrical circuit are functioning.If a pressure rise is not noted, there may be a fault with the solenoid or with the modulating valve.This test is carried out in order to determine if the solenoid coil on the modulating valve is energized.If a pressure rise is not noted, use a tag wire to check that the solenoid coil is energized.