OM3214 Operation - Section 32 Operator Cab and Controls Page 32-3 PEDALS When pedal (3) is partially depressed, dynamic retarding is activated (actuation is modulated). Pressing the pedal further applies full retarding. Dur- ing full retarding the service brakes also begin to apply. Completely depressing the pedal causes full application of both the dynamic retarding and the ser- vice brakes. SERVICE BRAKE PEDAL Service brake pedal (2, Figure 32-4) is a foot-operated pedal which applies the service brakes. NOTE: In some optional installations, the service brake pedal may not be present, because it is incorporated into a single pedal function with retarder pedal (3).
THROTTLE PEDAL Throttle pedal (4, Figure 32-4) is a foot-operated pedal which allows the operator to control the engine rpm, depending on the pedal depression. DYNAMIC RETARDER PEDAL Dynamic retarder pedal (3, Figure 32-4) 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 is used to slow and con- trol the speed of the truck. Refer to Grade/Speed Warning chart (8, Figure 32-1) to determine the maxi- mum safe truck speeds for descending various grades with a loaded truck.
Apply the service brakes only when dynamic retarding requires additional brak- ing force to slow the truck speed quickly and to com- pletely stop the truck. When dynamic retarding is activated, the engine rpm will automatically go to an advance rpm retard speed setting (usually 1250 rpm, see note below.) Dynamic retarding will be applied automatically if the speed of the truck reaches the predetermined overspeed retard setting. Dynamic retarding is available in FOR- WARD/REVERSE at all truck speeds above 0 kph (mph) but is available in NEUTRAL only when the truck speed is above 5 kph (3 mph). FIGURE 32-4. PEDALS 1. Cab Floor 2. Service Brake Pedal 3. Dynamic Retarder Pedal 4.
Throttle Pedal 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.