A landscaping contractor reported that a Komatsu PC60-8 mini excavator traveled very slowly. When climbing a slight grade, the machine almost stopped, and the engine bogged down. The other functions (boom, arm) worked normally.
The technician checked the pilot pressure, which was fine. He then tested the "Travel Motor" by disconnecting the hydraulic lines and capping them. The machine didn't move, confirming the issue was hydraulic, not mechanical. He connected a flow meter to the travel motor inlet. The flow was normal, but the pressure drop across the motor was high.
He removed the travel motor. It is a "Piston-Type" motor. Upon disassembling it, he found the "Piston Shoes" (slippers) were severely worn. The hydraulic oil had a "metallic" sheen. The wear was caused by the "Hydraulic Tank Breather" being missing. Without the breather, moisture and dust entered the tank, contaminating the oil and acting as an abrasive.
Furthermore, the "Shuttle Valve" (which switches between high and low speed) was stuck in the "Low Speed" position by debris. This prevented the motor from receiving full flow in high-speed mode.
The repair involved flushing the hydraulic system, replacing the travel motor rotating group, and installing a new breather cap. The shuttle valve was cleaned and freed. The system was refilled with fresh ISO 46 oil. The machine then traveled at normal speed and climbed slopes without issue.
