OM3215 10/04 Operating Instructions - Section 32 Page 32-3 PEDALS Throttle Pedal Service Brake Pedal The Throttle Pedal (4, Figure 32-3) is a foot-operated pedal which allows the operator to control engine RPM, depending on pedal depression. The Service Brake Pedal (2, Figure 32-3) is a foot-op- erated pedal which applies the service brakes. NOTE: In some OPTIONAL installations, this pedal may not be present, because it is incorporated into a single pedal function with the Retarder Pedal (3) .
Dynamic Retarder Pedal The Dynamic Retarder Pedal (3, Figure 32-3) is a foot-operated pedal which allows the operator to slow the truck and maintain a safe productive speed without the use of the service brakes. For normal truck opera- tion, only dynamic retarding should be used to slow and control the speed of the truck. The Grade/Speed Chart (8, Figure 32-1) should always be followed to de- termine MAXIMUM safe truck speeds for descending various grades with a loaded truck. Service brakes should be applied only when dynamic retarding re- quires additional braking force to slow the truck speed quickly and to bring the truck to a complete stop.
When dynamic retarding is in operation, the engine RPM will automatically go to an advance RPM retard speed setting (usually 1250 RPM)*. Dynamic retarding will be applied automatically, if the speed of the truck reaches the predetermined overspeed retard setting. Dynamic Retarding is available in FORWARD/RE- VERSE at all truck speeds above 0 mph/kph, but is available in NEUTRAL only when truck speed is above 3 mph (4.8 kph). FIGURE 32-4. PEDALS, VENTS 2. Service Brake Pedal 3. Retard Pedal 4. Throttle Pedal 5. Vents * NOTE: The exact engine speed in retarding may vary (1250 - 1650 RPM) due to the temperature of certain components; this is controlled by the Statex III control system.
Optional - Dual Function / Single Pedal The Dynamic Retarding/Brake Pedal is a single foot-operated pedal which controls both retarding and service brake functions. Thus, the operator must first apply, and maintain, full dynamic retarding in order to apply the service brakes. When the pedal is partially depressed, the dynamic re- tarding is actuated (actuation is modulated). As the pedal is further depressed, dynamic retarding is fully applied; then, while maintaining full retarding, the ser- vice brakes are actuated (a slight increase in pedal re- sistance will be felt) through a hydraulic valve, which modulates pressure to the service brakes.
Completely depressing the pedal causes full application of both dynamic retarding AND the service brakes .