Retarding System Schematics
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| Illustration 1 | g03401737 |
Schematic connections for Retarder switch (located on a lever on the right side of the steering column). | |
Retarding System Function
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| Illustration 2 | g03481797 |
Location of the manual Retarder lever | |
The retarding system applies a counter force to the transmission input shaft. The force is used to maintain the speed of the truck while driving downhill. The assisted manual retarding control allows the operator to use the manual "retard" lever to select the desired speed. The system reduces the need for the application of the brakes.
The retarder housing and the stator are bolted to the Torque Converter Housing. The retarder housing and the stator do not rotate. The rotor is splined to the Transmission Input Shaft.
The resistance of the stationary stator vanes to the moving oil creates a pressure that slows the rotation of the rotor. Increasing pressure in the retarder housing will increase the resistance to rotation applied to the rotor. Increasing pressure in the retarder housing can be due to an increase in rotor speed as the momentum of the machine increases. Increasing pressure in the retarder housing is due to an increased volume and pressure of the oil in the retarder housing. This condition occurs as the operator selects a greater amount of retarder activation.
The retarder control lever in the cab operates the hydraulic retarder control valve. The hydraulic retarder control valve is a proportional solenoid valve. The valve is energized to varying states by the Transmission/Chassis ECM, creating four levels of oil pressure inside the retarder housing.
The four pressure levels are attained as the hydraulic retarder control valve increases the volume and pressure of the oil inside the housing as the control lever is moved from OFF, to MINIMUM, to MEDIUM, and to MAXIMUM.
The status of the hydraulic retarding torque is displayed on the LCD display. When the system is commanded, the manual retarding indicator is displayed as an amber symbol. When a fault has occurred involving the retarding system, the indicator lamp is a solid amber color.
If the system experiences an erratic, intermittent, or incorrect signal from the retarder lever, the ECM defaults the system to the high retarding position. A level 2 event code warning is issued by the ECM, as well. The operator will also be alerted by the activation of the retarding symbol on the instrument cluster. The symbol will glow a solid amber color during a faulted state of the retarding system (see Illustration 3, symbol indicated by arrow).
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| Illustration 3 | g03481802 |
Location of retarding fault indicator. (Lower left side of instrument cluster.) | |
Note: The retarding guidelines are located on a film inside the cab and in the Operation and Maintenance Manual.