Fault Phenomenon: SANY SKT90 wide body mining truck transmission operates only in a single speed range, unable to continuously vary.

Troubleshooting Process:
– Checked variable mechanism: variable motor swashplate actuating piston seized.
– Checked control oil pressure: insufficient pilot control pressure.
– Checked feedback rod: mechanical feedback rod detached.
– Checked oil quality: severely contaminated transmission fluid.

Root Cause: The swashplate actuator inside the transmission variable motor is stuck at the limit position due to metal debris in the oil, unable to adjust displacement based on load.

Required Parts: Disassemble and repair variable motor or replace assembly.