A gravel yard reported that a Lonking LG855N wheel loader would not shift into low range (1st gear). The machine would only start and drive in high range (2nd gear), making it impossible to climb steep stockpile ramps. The operator stated the gear selector lever felt loose.
The technician first checked the transmission control valve on the side of the gearbox. This model uses a mechanical cable to shift a spool valve that directs oil to the high and low clutch packs. The cable was intact, but the mounting bracket welded to the transmission housing had cracked and bent. This prevented the cable from pulling the spool valve fully into the "Low" position. The bracket was re-welded, but the machine still refused to shift.
Further inspection revealed that the inching valve (a valve that reduces pressure for smooth gear changes) was seized in the "inched" position due to rust. The inching valve is mechanically linked to the brake pedal. When the operator presses the brake, the inching valve dumps transmission pressure. If this valve is stuck partially open, the pressure is too low to engage the Low clutch pack, which requires higher pressure than the High clutch pack.
The technician disassembled the inching valve, cleaned the spool with fine emery paper to remove the rust, and lubricated it with fresh transmission fluid. After reassembly, the pressure was restored, and the loader shifted smoothly into low range, allowing it to climb the ramps with full torque.
