Troubleshooting Caterpillar 773G Haul Truck That Won’t Move

[MikePhua]

Problem Description
A user reported that their Caterpillar 773G haul truck was not moving despite the engine running normally. The issue affected both forward and reverse motion, leaving the machine stuck and inoperable.
Potential Causes
Community members suggested several common causes for the problem. These included issues with the transmission system, such as low hydraulic pressure, malfunctioning transmission control valves, or a faulty torque converter. Electrical problems affecting control circuits were also considered.
Hydraulic and Transmission Checks
Advice focused on inspecting hydraulic fluid levels and conditions, as contaminated or low fluid can prevent transmission engagement. Checking for leaks, damaged hoses, or clogged filters was recommended. Some users suggested testing the transmission control valves and solenoids for proper function.
Electrical System and Sensors
Users highlighted the importance of verifying sensor inputs and electrical connections. Faulty neutral safety switches, wiring problems, or sensor failures could prevent the truck from recognizing commands to move. Diagnosing with appropriate electronic tools was advised.
Mechanical Inspection
Mechanical causes such as worn clutches or damaged drive components were discussed as possible reasons for immobility. A thorough mechanical inspection was suggested if hydraulic and electrical systems were found to be in good order.
Conclusion
When a CAT 773G haul truck won’t move, it’s important to systematically check hydraulic pressure, transmission components, electrical controls, and mechanical parts. Careful troubleshooting and maintenance are essential to restore proper operation and minimize downtime.