. OPERATION OPERATION OPERATION OPERATION and operate retarder control lever (2) to slow the machine down. 3 - 96 1. Before startin g to t ravel downhill, release a ccelerator peda l (1) 2. Move t he gea r shif t leve r to a position (5, 4 , 3, 2) that matches the maximum speed brake performance. 3. When travelin g downhil l, operate retarder c ontrol lever (2), run the engine at a speed o f at least 1800 rpm , and travel so that the retarder br ake oil te mperature gauge is in the white range.