https://www.truck-manuals.net/mack/ OPERATION 173 MACK T310 Shifting Instructions
CAUTION Make sure air pressure is at least 90 psi and unit is warmed 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 T310 unit is a range-shifted transmission which has 10 forward "highway" speeds. This transmission features a LO and HI auxiliary compound section controlled by an air shift range selector located on the shift lever. The compound section is equipped with a synchronizer to facilitate LO-/HI- range shifting. The LO range provides five low ratios. Never attempt to move the vehicle from a stopped position in any gear higher than fourth speed gear. Depending on load, grade, or road conditions, it may be necessary to start in first, second, third or fourth speed gears. In HI range there are five forward gears that can be shifted in the standard manner. Always remember, however, to double clutch whether moving up or down through these gears. Reverse gear can be used in LO range only. Upshift - With the shift lever in NEUTRAL, flip the air shift range selector down to LO range. Then shift the transmission into first gear. Shift up to second, third, fourth and fifth speed gears, double clutching between the gears. When maximum engine RPM has been reached in fifth gear, flip the air shift range selector up to HI range (preselect). Then move the shift lever through NEUTRAL to sixth gear. As the shift lever passes through NEUTRAL, the transmission is placed into Hi range. Continue following the normal sequence (7-8-9-10), being sure to double clutch from one gear to the next. Downshift — Shift from 10th speed gear down through the HI range (9-8-7-6), double clutching through each gear. While still in sixth speed gear, flip the air shift range selector down to LO range (preselect). Then move the shift lever through NEUTRAL to fifth speed gear. As the shift lever passes through NEUTRAL, the transmission is placed into LO range. Then, shift down to fourth, third, second and first speed gears, double clutching between all gears.
