Troubleshooting the Power Train
Problem: The transmission will not shift into any gear from the Neutral position
Probable Causes
- Low Oil Level
- Low battery voltage
- Wiring harness connections
- Transmission control (shifter or forward, neutral, reverse toggle switch)
- Electrical problem with the clutch pedal
- Main relief valve
- Transmission oil pump
- Rotating seal leakage in the transmission
- Multiple ECPC valves are malfunctioning.
- The parking brake system is malfunctioning.
Problem: The transmission has lost a single gear
Probable Causes
- The wiring harness for the transmission control
- Transmission control (shifter or forward, neutral, reverse toggle switch)
- Electronic control module
Problem: The motor grader has lost multiple forward/reverse gear selections
Probable Causes
- Torsional coupling failure
- Wiring harness
- The ECPC valve is malfunctioning.
- Transmission control (shifter or forward, neutral, reverse toggle switch)
- Electronic control module
- Internal transmission problem
- Active diagnostics on the Transmission/Chassis ECM.
Note: Before performing test procedures that involve running the engine, check the magnetic screens in the transmission for bolts or metallic debris. Metallic debris could indicate a torsional coupling failure.
Note: If the transmission will shift into First speed forward, Fifth speed forward, or First speed reverse, the parking brake may be engaged. There could also be an electrical fault in the parking brake system.
Problem: The motor grader creeps when the clutch pedal is fully depressed
Probable Causes
- Calibration for the clutch pedal
- The ECPC valve requires calibration.
- The ECPC valve is malfunctioning.
- Wiring harness for the ECPC valve
- Wiring harness for the transmission
- Contamination
- Driver in the electronic control module
- Internal clutch drag
Problem: When the transmission shifts a hesitation occurs
Probable Causes
- The ECPC valve requires calibration.
- The ECPC valve is malfunctioning.
- Contamination in the transmission control valve
- Oil temperature sensor
- Drivers in the electronic control module
- Speed sensors
- Internal seal leakage on the transmission
- Internal pump leakage
- Main relief valve
- Differential lock valve
- Communication link between engine and transmission
- The pump is causing aeration.
Problem: The transmission shifts are harsh
Probable Causes
- Transmission speed sensor
- Wiring harness for the transmission speed sensor
- Communication link between engine and transmission
- Oil temperature sensor
- The ECPC valve requires calibration.
- The ECPC valve is malfunctioning.
- Broken spring in the main relief valve
- A spool in the main relief valve sticks.
- The piston on a clutch sticks.
Problem: The transmission shifts are sluggish
Probable Causes
- Worn clutches
- The ECPC valve requires calibration.
- The ECPC valve is malfunctioning.
- Slow clutch disengagement
- The calibration of the proportional solenoid valve
- The parking brake system is malfunctioning.
Problem: The transmission shifts at the wrong point when the autoshift control is in the ON position
Probable Causes
- Transmission intermediate speed sensor
- Transmission input speed sensor
- Transmission output speed sensor
- The electronic control module has the wrong transmission configuration code.
Problem: The transmission does not shift into all the gears when the autoshift is in the ON position
Probable Causes
- Transmission intermediate speed sensor
- Transmission input speed sensor
- Transmission output speed sensor
- The top gear limit is set.
- The operator override is selected.
Problem: The transmission shifts into the wrong gear when the autoshift is in the ON position
Probable Causes
- Transmission intermediate speed sensor
- Transmission input speed sensor
- Transmission output speed sensor
- The wiring harness for the ECPC valve is bad.
- The wiring harness for the Transmission/Chassis ECM is bad.
Troubleshooting the Parking Brake System
Problem: The parking brake does not hold the machine stationary.
Probable Causes
- The brake linings for the parking brake are worn.
- There is grease or oil on the brake lining.
- The parking brake must be adjusted.
Problem: The parking brake does not engage when the parking brake switch is actuated.
Probable Causes
- The parking brake switch is faulty.
- The parking brake solenoid is not operating properly.
- The main relief valve setting for the transmission is incorrect.
- The piston seals are damaged or broken.
Transmission does not shift into correct gear when autoshift is OFF
This behavior may not be expected by an operator. The following features (which automatically shift the transmission when the machine is in manual shift mode) are new to M3 Motor Graders:
Probable Causes
- Speed match
- Optimized gear
- Antistall
- Underspeed
- Upshift inhibit
Upshifts the transmission if the engine speed in gear is greater than 2500 RPM to avoid engine overspeed. Will automatically downshift the machine once engine speed falls below 2150 RPM. Same downhill grades.
Downshifts the transmission if the engine speed in gear is lesser than low idle to avoid engine excessive operation below low idle. Will automatically upshift the machine once engine returns to Low idle. OMM overrides (2 downshift conditions) lug back from high engine speed at 1200 rpm under load lug.
Neutralizes the transmission if the engine speed is lesser than 600 RPM to avoid engine excessive operation below low idle or engine stall. Will require operator to cycle the FNR switch to N before relaunching the machine. Will log an event.
Matches the transmission launch gear to current machine speed when the inching pedal is depressed or the FNR is in the N position. Speed match gear selection prevents excessive engine lug, engine overspeed, or excessive clutch energy (behaves similar to auto-shift).
Matches the transmission max shuttle shift gear to an appropriate range based on current machine velocity and operating grade. Optimized gear selection prevents excessive engine lug or clutch energy.