THEORY OF OPERATION - CONTINUED
POWERTRAIN - CONTINUED
To manually shift transmission, autoshift switch must be in MANUAL position (TM 5-3805-291-10). Shifting
transmission is powertrain ECM's main function. Powertrain ECM interprets changes in switch position and shifts
Operator can set transmission direction with transmission direction and shift lever. Selected gear and direction will
be displayed on speedometer/tachometer dashboard display.
Transmission direction and shift lever is a sealed unit mounted on steering column which allows operators to select
speed range by rotating control lever. Operators can select direction by moving transmission direction and shift
lever forward or backward. Transmission will remain in selected direction until lever is moved forward or back-
ward. Transmission will remain in selected speed until lever is rotated to different speed.
When transmission downshift switch (TM 5-3805-291-10) is depressed, it signals powertrain ECM to downshift
transmission by one speed. If second speed forward or second speed reverse is selected, transmission will shift to
first speed when switch is depressed. Transmission will remain in first speed until transmission direction and shift
lever is shifted to opposite direction or to NEUTRAL.
When engine start switch is turned from OFF to ON, powertrain ECM is activated. When powertrain ECM is first
activated, all clutch solenoid modulating valves are de-energized regardless of transmission direction and shift
lever or transmission direction control switch position. Powertrain ECM then determines if transmission direction
and shift lever is in NEUTRAL and disables transmission if NEUTRAL is NOT selected. Lever must be in NEU-
TRAL position before direction can be selected. Powertrain ECM activates start relay and allows engine to start if
lever is in NEUTRAL. Powertrain ECM allows initial selected speed to be changed if lever is in NEUTRAL.
Automatic Shift Function.
N OT E
If downshift would cause an engine overspeed condition, the powertrain ECM will prevent the down-
shift from occurring.
The setting of the transmission direction and shift lever will limit the top gear.
Transmission can be shifted automatically. There are two modes of automatic operation: "1-4" and "2-4". Auto-
matic operation mode is represented by two numbers separated by a dash. First number indicates transmission
speed when transmission is placed in gear and second number indicates highest transmission speed when machine
For example, place autoshift control switch in "2-4" position. Machine will automatically shift into second gear
when transmission is placed in gear. Transmission will automatically upshift into fourth gear as machine acceler-
Use transmission downshift switch located on lift lever on right side of operator's compartment to downshift trans-
mission (TM 5-3805-291-10). This switch is normally used to downshift from second speed to first speed to load a
bucket. Transmission will remain in downshifted gear for three seconds after switch is released, then automatic
shifting will resume. If transmission is downshifted to first speed, machine remains there until there is a direction