https://www.truck-manuals.net/mack/ OPERATION 165 MACK TM309 Shifting Instructions
CAUTION Make sure air pressure is at least 90 psi and unit is warmed before shifting the transmission. To avoid transmission damage, do NOT change range while moving in REVERSE. Use of the clutch brake is for shifting into first and reverse gears only. Do not use the clutch brake to shift out of gear. Be careful not to overspeed the engine during downshifting. Damage to powertrain components can result.
The TM309 is a non-synchronized transmission having a total of nine speeds (6+3) with an air shifted non-synchronized compound section. This LO and HI auxiliary compound section is controlled by an air-shift range selector valve located on the shift lever. The LO range has three low gear ratios. In HI range there are six forward gears which can be shifted in the normal manner, but remember to double-clutch whether moving up or down through the gears. For normal highway use, start in HI range, first gear and shift through second, third, fourth, fifth and sixth. The ratio step between fifth and sixth is smaller than all the other ratio steps. The three gears in LO range are designed for off-highway use and in slow-moving operations (curb pouring, material spreading, heavy load, steep grade). Only start in the lowest gear necessary to move the vehicle. The extreme LO gear (1st low) is intended for vehicular speed control and not for torque multiplication.For normal highway use, start in HI range, first gear and shift through second, third, fourth, fifth and sixth. The ratio step between fifth and sixth is smaller than all the other ratio steps. The three gears in LO range are designed for off-highway use and in slow-moving operations (curb pouring, material spreading, heavy load, steep grade). Only start in the lowest gear necessary to move the vehicle. The extreme LO gear (1st low) is intended for vehicular speed control and not for torque multiplication. Reverse — Reverse can be used in LO or HI range. To make a range shift in reverse, bring the truck to a complete stop. Flip the range selector lever to range desired (preselect). Move the shift lever out of reverse through NEUTRAL and then back into reverse again. As the lever moves through NEUTRAL, the range shift will be completed.
