Fault Phenomenon: JLG 450AJ articulating boom aerial work platform with the platform raised, travel speed is extremely slow, accompanied by abnormal noise.

Troubleshooting Process:
– Checked drive motor: motor no signs of burning.
– Checked gearbox: gearbox oil level normal.
– Checked proportional valve: valve spool stuck.
– Checked axle engagement: axle not switched to wide track mode (if applicable).

Root Cause: The drive proportional valve spool is stuck, causing limited flow; or the axle lock mechanism is not fully unlocked.

Required Parts: Drive proportional valve assembly.