Mack Tm308 Shifting Instructions - Mack Granite GU Series Operator's Handbook Manual

MACK TM308 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 TM308 is a non-synchronized transmission having a total of eight speeds
(6+2) with a non-synchronized air shifted 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 two 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 two gears in LO range are designed for
off-highway use and in slow-moving operations (curb pouring, material
spreading, heavy load, steep grade).
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.
OPERATION 195