THEORY OF OPERATION - CONTINUED
POWERTRAIN - CONTINUED
Parking Brake Function.
Parking brake function prevents an operator from operating machine while parking brake is engaged. Driving
through parking brake causes accelerated wear to parking brake friction components.
When parking brake control is disengaged, transmission will shift normally. When parking brake control is
engaged, transmission will not shift out of NEUTRAL to first speed forward or first speed reverse. If transmission
is in first speed forward or first speed reverse and parking brake is moved to engaged position, transmission will
shift into NEUTRAL. All transmission clutch modulating valves are de-energized. If transmission is in second
speed forward or third speed forward, transmission will remain engaged.
Parking brake function activates a warning on Messenger whenever parking brake is engaged. Parking brake indi-
cator will flash (TM 5-3805-291-10).
When parking brake is engaged and transmission is in first speed, powertrain ECM shifts transmission to NEU-
TRAL and sends parking brake status to Messenger via CAT Data Link. When parking brake is engaged, alert indi-
cator for parking brake flashes on Messenger (TM 5-3805-291-10). If operator selects FORWARD or REVERSE
and parking brake is engaged, Messenger causes parking break indicator and action lamp to flash, and action alarm
Driving Through Parking Brake.
Driving through parking brake will damage parking brake and other components. Always come to a com-
plete stop before applying parking brake.
Powertrain ECM will allow operator to drive through parking brake. Machine should be moved only for a
To drive through parking brake, operator must select first speed forward or reverse, and move transmission
shift lever to NEUTRAL, then move transmission shift lever to previous selected direction.
Backup Alarm Function. Backup alarm function alerts surrounding personnel that machine is backing up. Backup
alarm is an output of powertrain ECM, which activates backup alarm relay when transmission shift lever is in
REVERSE. Backup alarm relay then activates backup alarm. Backup alarm receives a +battery signal from powertrain
ECM when backup alarm is activated. Backup alarm is connected to powertrain ECM connector contact J1-12 of pow-
Secondary Steering. Secondary steering system provides steering control of machine when primary steering system has
failed. Secondary steering system is intended for emergency use only.