The normal shiftpoints for Articulated Trucks are listed in the following tables. To help protect the power train, certain shifting restrictions exist. The major shifting restrictions are described in the following paragraphs.
Engine overspeed protection exists. If engine speed increases to approximately 2900 rpm, the transmission will upshift one gear. And if in top gear, the lockup clutch will be disengaged which places the machine in torque converter drive.
Engine underspeed protection exists. If engine speed decreases to approximately 750 rpm, the transmission will downshift one gear.
Retarder protection exists. When the retarder is applied, all shift points are elevated. This increases engine speed which causes more oil to flow through the retarder. For upshifts, the shiftpoint is elevated approximately 250 engine rpm. For downshifts, the shiftpoint is elevated approximately 75 engine rpm.
Transmission protection exists. For 2.3 seconds after a shift, the transmission will not shift in the opposite direction. For example, after an upshift, a downshift is not allowed until 2.3 seconds have passed. This is called the anti-hunt feature and eliminates shifting due to minor ground speed fluctuations near a shiftpoint. The 2.3 second restriction allows conditions to stabilize before an opposite shift. If any brake is applied, the anti-hunt feature is canceled and transmission downshifts occur as conditions demand.
Neutral coast protection exists. When NEUTRAL is selected at the shift lever while the transmission is in a forward gear, the transmission will only be shifted to neutral when ground speed is 5 mph or less. If the machine is coasting with the transmission in NEUTRAL, the transmission will not shift into a forward gear. The transmission will only shift to REVERSE when ground speed is less than 3 mph.