A municipal water department reported that a Case 580N backhoe loader drifted severely to the right when driving on the highway at speed. The operator had to constantly hold the steering wheel 15 degrees off-center to keep the machine straight. Additionally, when loading wet clay into a trench, the front wheels spun freely, offering zero traction, even though the rear wheels dug in perfectly.
The technician first investigated the steering issue. In the 580N, the front axle is both driven and steered. He checked the steering orbitrol (steering control unit) and found that the priority flow from the hydraulic pump was erratic. He removed the "Priority Flow Divider Valve" mounted on the main pump. The internal priority spool, which guarantees steering flow before sending flow to the loader/backhoe implements, had seized in the "implements" position due to a sliver of O-ring debris. The steering circuit was being starved of flow, and the orbitrol was scavenging oil from the front axle steering cylinders, causing the wheels to turn right.
The lack of front traction was directly related. The 580N uses a "Front Axle Disconnect Clutch" controlled by a pilot pressure line off the steering priority circuit. Because the priority valve was seized and steering pressure was low, the front axle disconnect clutch was never fully engaged. The clutch discs were slipping constantly under the road speed, causing the severe drift, and when under load in the trench, the front axle could not transmit torque because the clutch was partially disengaged and burnt out.
The repair involved freeing and cleaning the priority flow divider valve spool, replacing the damaged O-ring, and replacing the completely burnt front axle disconnect clutch pack. The hydraulic system was flushed, and fresh oil and filters were installed. After reassembly, the steering tracked perfectly straight, and the front axle engaged and provided full traction under load.
