Prior to starting with checks on the modulating valves, use Caterpillar ET in order to diagnose any fault codes that may be present. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, KENR5903, "Power Train Electronic Control System".
After checking for fault codes, run a calibration of the transmission. Refer to Systems Operation, Troubleshooting, Testing and Adjusting, KENR5903, "Transmission - Calibrate".
Testing The Modulating Valves
 | |
| Illustration 1 | g01704954 |
Modulating Valves (Electronic Clutch Pressure Control) | |
| TH48-E70 SPEED SELECTION | |
|---|---|
| SPEED | ENGAGED CLUTCHES (= ENERGIZED VALVES) |
| Park | 4 and 6 |
| Neutral | 1 |
| Stall | 1, 4 and 6 |
| First Gear Forward | 2 and 6 |
| Second Gear Forward | 1 and 6 |
| Third Gear Forward | 3 and 6 |
| Fourth Gear Forward | 1 and 5 |
| Fifth Gear Forward | 3 and 5 |
| Sixth Gear Forward | 1 and 4 |
| Seventh Gear Forward | 3 and 4 |
The 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 top of the transmission.
With a stationary machine, the pressure of the oil in the transmission clutches can only be tested on clutch 1. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures".
If the pressure for clutch 1 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 Specification, 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.
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 5000 kPa (0 to 800 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 Specifications, Systems Operation, Testing and Adjusting, "Power Train Pressures" and Systems Operation, Troubleshooting, Testing and Adjusting, KENR5903, "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. If the tag wire is attracted to the solenoid coil, this indicates that the solenoid coil is energized. The problem is in the solenoid cartridge. The problem could be a bent solenoid stem, a screen that is dirty or plugged, or a spring that is weak or broken. Repair the electronic clutch pressure control modulating valve or replace electronic clutch pressure control modulating valve.
If the tag wire does not indicate that the solenoid coil is energized, the problem is in the electrical circuit.
If the solenoid does not appear to function, disconnect the connector for the solenoid. Check the resistance of the windings of the coil in the solenoid.
The resistance of the windings in the solenoid should be 8.7Ω ± 0.4Ω.
If the resistance of the windings is outside the specifications replace the solenoid.
ReferenceFor additional information about the electronic clutch pressure control modulating valves, refer to Specifications, Systems Operation, Testing and Adjusting, "Modulating Valves (Electronic Clutch Pressure Control)".
ReferenceFor additional information about electrical system troubleshooting, refer to Systems Operation, Troubleshooting, Testing and Adjusting, KENR5903, "Power Train Electronic Contol System".