Fault Phenomenon: JLG 3394RT scissor lift aerial work platform cannot switch to four-wheel drive mode, only two-wheel drive works.

Troubleshooting Process:
– Checked shift solenoid valve: valve stuck.
– Checked hydraulic motors: motor internal leakage.
– Checked mechanical gear sleeve: gear sleeve worn.
– Checked switch: switch failed.

Root Cause: The four-wheel drive shift solenoid valve is stuck or the mechanical gear sleeve is worn.

Required Parts: Four-wheel drive shift solenoid valve or gear sleeve.