https://www.truck-manuals.net/mack/ 180 OPERATION MACK T313-T313L-T313LR Shifting Instructions
CAUTION Make sure air pressure is at least 90 psi and unit is at operating temperature before making range shifts. Always start in LO range. This also applies to dynamometer testing. When the truck is stationary, do NOT shift into HI range and then start moving the truck. Otherwise, damage to the synchronizer may result.
The T313(L)(LR) is a range-shifted transmission with 12 forward highway speeds and an extra LO gear in the LO range. LO and HI ranges are controlled by an air-shift range selector. Note: When making a SPLIT SHIFT from gear to gear, the splitter switch must not be actuated, either up or down, until the main box is in NEUTRAL. When making a SPLIT SHIFT in the same gear to a preselected gear, especially under a heavy load, the splitter will not shift until the driveline torque is relieved. This can be done by depressing the clutch pedal and releasing it, or by backing off the throttle and reapplying it. The splitter switch must not be actuated, either up or down, until IMMEDIATELY before the driveline torque is relieved. When making a RANGE SHIFT, it is important to preselect the range shift. This means that the range selector must be moved to its next position (up or down) BEFORE the gearshift lever is moved. Then move the gearshift lever through NEUTRAL to the next desired gear position. As the lever passes through NEUTRAL, the range shift will be completed.
CAUTION Do not "play" with the splitter and range selector tabs at a stop light, flipping from high to low range or HI-LO split. These controls are not intended for entertainment. Such activity can adversely impact the life of the transmission.
Upshift — For purposes of explaining the shifting procedures through ALL gears, assume that the vehicle has a full load and will climb a slight grade. Before moving the vehicle, the range selector must be in LO range and the splitter switch in LO-split. With the shift lever in NEUTRAL, move the splitter to LO-split (if needed), then the range to LO range (if needed).
