(6) RETARDER PEDAL The Retarder Pedal is the left pedal of the three pedals and should be used by the operator to slow the truck during normal operation and to maintain a safe productive speed while decending grades. When the retarder pedal is activated, only the rear oil-cooled brakes are applied; the front brakes are not applied. The amount of retarding is controlled by how far the operator depresses the pedal and with full application may be used for non-emergency stops. Retarder Operation The operator should use the retarder pedal instead of the service brake pedal for slowing the truck and for non-emergency stops whenever speed and load condi- tions permit.
Using the retarder saves front brake wear and provides better steering control. When approaching a descending grade, the operator should slow the truck and select the proper transmission gear range to maintain an engine speed of 1650 -- 2350 RPM (green area on tachometer) and the brake oil temperature below 250 o F (121 o C) during retarder operation. Refer to the Grade/Speed decal in the cab above the windshield. When descending a grade, the operator should apply the retarder pedal and observe both the Tachometer and the Brake Oil Tem- perature Gauge .
The engine RPM must be maintained at 1650 -- 2350 RPM (green area on tachometer) and the Brake Oil Temperature must be maintained below 250 o F (121 o C). If the operator observes that either the maximum engine speed of 2350 RPM or the Brake Oil Temperature of 250 o F (121 o C) are about to be exceeded, the operator should immediately move the transmission range selector to the next lower range and apply the service brakes until the truck is slowed to a speed which will permit the transmission to downshift to the gear range selected. Continue this procedure to downshift to the required gear range to maintain engine speed at 1650 -- 2350 RPM and brake oil temperature below 250 o F (121 o C).
The service brakes should be used only long enough to slow the truck to allow the transmission to downshift. When the proper gear range is attained, continue using the retarder to maintain a safe, productive speed. If brake oil temperature exceeds 250 o F (121 o C), the Brake Oil Temperature Warning light will turn on. As quickly as safety will permit, bring the truck to a complete stop away from traffic, move transmission range selector to "Neutral", apply the parking brake, and run engine at high idle. Continue to run engine at high idle until Brake Oil Temperature Warning light turns off and brake oil temperature cools to below 250 o F (121 o C).
If temperature does not return to this range within a few minutes, report the condition immediately to maintenance personnel and wait for further instructions before moving truck. HB4021 6/95 Operator Controls HB4-3