Fault Phenomenon: Foton Raysta L14 transmission functions normally when cold. During heavy-load driving (operating temperature), the transmission automatically jumps out of gear, power transmission is interrupted, and eventually fails.

Troubleshooting Process:
– Checked transmission oil level: level normal.
– Checked shift linkage: linkage clearance normal.
– Checked synchronizer: wear normal.
– Measured transmission axial clearance at operating temperature: found excessive clearance.

Root Cause: Transmission gear bearings wear due to heat, causing axial movement and gear jump-out.

Required Parts: Transmission bearings and gear set.