Shifting a Manual Transmission

Depending on the transmission model, the gear split may vary from 400 to 500 rpm. The electronic governor provides almost no overrun capability and if the transmission is downshifted too early, a temporary loss of pulling power will be experienced until the engine speed falls below rated speed.

In general, when using a 7- or 9-speed transmission, the operator should always downshift between 1150 and 1250 rpm for the DD13 and between 1000 and 1100 rpm for the DD15. This is true even on steep grades with heavy loads. When using an 18-, 15-, or 13-speed transmission, the operator will need to downshift at an rpm that allows "less than rated" rpm before throttle application in the next gear down. The operator may want to limit engine speed to 1900 rpm in all gears as fuel economy is not as efficient above 1800 rpm.