A construction crew reported that a Komatsu PC200-8M0 excavator pulled to the right when traveling straight. The right track moved slower than the left, and the travel motor housing was hot to touch after 30 minutes of operation.
The technician tested the pilot pressure, which was normal. He then swapped the two "Travel Motor Hoses" (left to right) at the main control valve. If the problem moved to the left track, it would be a valve issue. However, the slow speed remained on the right track, confirming a motor issue.
He removed the right travel motor cover. Komatsu travel motors use a "High-Low Speed" shifting mechanism. He checked the "Speed Change Valve." It was stuck in the "Low Speed" position by a small piece of rubber seal debris. This caused the motor to always operate in high torque (low speed) mode, creating the speed mismatch.
Furthermore, the "Travel Brake Piston" seals were worn. The brake piston is hydraulically released when the travel lever is moved. The worn seals allowed high-pressure oil to leak into the brake housing. This leakage generated heat (explaining the hot housing) and also prevented the brake from fully releasing, creating a drag that further slowed the track.
The repair involved cleaning the speed change valve spool and replacing the brake piston seals. The travel motor case drain line was flushed. After reassembly, both tracks traveled at the same speed, and the motor housing temperature remained stable.
