Mack T309, T309L And T309Lr Shifting Instructions - Mack Granite GU Series Operator's Handbook Manual

204 OPERATION
MACK T309, T309L and T309LR 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 T309 unit is a range-shifted transmission which has eight forward highway
speeds plus an extra LO speed gear in the LO range. 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 second gear. Depending on the
load, grade or road conditions, it may be necessary to start in LO speed gear
or first-second gears. Note that LO speed gear was designed for off-highway
use such as paving, material spreading or heavy load/steep grade conditions.
The HI range has four forward gears that can be shifted in the standard
manner. Remember, however, to double-clutch when moving up or down
through these gears.
REVERSE can be used in LO range only.
Upshift — Under normal highway conditions, with shift lever in NEUTRAL, flip
air-shift range selector to LO range, then shift the transmission into first gear
(see shift pattern). Shift through second, third and fourth, double-clutching
between gears. When maximum RPM is reached in fourth gear, flip air-shift
range selector to HI range (preselect) and then move shift lever through
NEUTRAL to fifth gear. As the shift lever passes through NEUTRAL, it will
put the transmission in HI range. Now continue double-clutching through
sixth, seventh and eighth gears.
CAUTION
Do NOT move the air-shift range selector while moving in REVERSE. Also, when
the truck is stationary, do NOT shift into HI range and then start moving the truck.
Damage to the synchronizer may result.