UNDERCARRIAGE AR 3905107 - Caterpillar

Automatic Retarder Control (ARC) (2) - Push the top half of the switch in order to select the ON position for the ARC system. This allows the machine to maintain a constant downhill speed. Push the bottom half of the switch in order to select the OFF position for the ARC system. When the proper gear is selected during ARC operation, vehicle speed and engine speed will be automatically regulated. If necessary, use the manual retarder control in order to apply more retarding force during the operation of ARC.The ARC should remain in the ON position during normal operation. When you place switch (2) in the OFF position, the ARC will not control engine speed during normal operation. However, if the engine speed becomes too high, the ARC will perform overspeed protection.Engine Overspeed Protection
This machine is equipped with automatic engine overspeed protection. If the engine speed reaches 2475 rpm, the ARC system will automatically engage, regardless of the position of the ARC switch. In order to prevent further engine overspeed, the transmission will upshift one gear if the engine speed reaches 2700 rpm and the transmission is in the same actual gear as the selected gear on the transmission control.Retarding Guidelines (Film)
Retarding performance charts provide an indication of the energy absorption capability of a given truck powertrain on a specified continuous, and less than 610 m (2000 ft) decline. Retarding performance charts serve to indicate the correct transmission gear selection and ground speed that should be used on a given grade to avoid situations which may result in machine overspeed and damage to the machine. Retarding performance charts do not give an indication of the ability of the truck to stop or the ability of the truck to remain stationary on the grades that are listed on the chart.
Illustration 3 g02783778
770G guidelines
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772G guidelines
The film that shows the retarding capabilities for your machine configuration is located on the inside of the cab.
Maximum Operating Weight - The maximum operating weight of a loaded Off-Highway Truck
Transmission Gear for the Downgrade - The selected gear for downhill travel
Downhill Slope Percentage - The percentage value of the slope for downhill travel
Distance of the Downgrade - The distance of the slope for downhill travelThe retarding capabilities that are listed on this film are based on an ambient temperature of 32 °C (90 °F).The actual retarding capabilities for each gear will vary depending on the following conditions: outside temperatures, rolling resistance, load, the condition of the cooling system, tire size and altitude.Retarding Information and Conditions
Selection of the proper gear is essential for effective operation of the retarder system. Refer to the film for retarding guidelines in order to select the proper gear.Select the proper gear on the transmission control before you start down the grade. The actual gear should also match the selected gear before you start down the grade. For more information on the transmission control, refer to Operation and Maintenance Manual, "Operator Controls".When the film does not address the current conditions, use the