https://www.truck-manuals.net/mack/ 170 OPERATION Downshift — To downshift the T309, shift from eighth to seventh, sixth and fifth (HI range), double-clutching between gears. While still in fifth gear, flip the air-shift range selector to LO range (preselect), then shift through NEUTRAL to fourth gear. As you shift through NEUTRAL, the range shift to LO will be completed. Move the shift lever to third, second and first, double-clutching between gears. T309 and T309L Reverse — Reverse can be used in LO range only. T309LR Reverse — Reverse can be used in LO and HI range. To make a range shift in reverse, bring the truck to a complete stop. Flip the range selector to the 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.
CAUTION To avoid transmission damage, do NOT change range while moving in REVERSE.
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