Replacing an excavator slewing drive is a major repair that requires precision, the right tools, and a strong emphasis on safety. While this task is best left to experienced mechanics, understanding the process helps equipment owners and managers appreciate the complexity involved and ensure the job is done correctly.

This guide outlines the key steps for a successful slewing drive replacement.

SAFETY FIRST!

• Secure the Machine: Park the excavator on a firm, level surface. Lower the attachment fully to the ground.

• Disable the Machine: Engage all safety locks. Release hydraulic pressure from the entire system. Disconnect the battery to prevent any accidental ignition or movement.

• Use Proper Support: The upper structure is extremely heavy. Use certified, weight-rated stands and blocks to securely support it before disassembly.

• PPE: Always wear appropriate Personal Protective Equipment (PPE) including safety glasses, gloves, and steel-toe boots.

The Replacement Process: A Step-by-Step Overview

1. Preparation and Disassembly:

• Obtain the service manual for your specific excavator model. It is an indispensable resource for torque specs and procedures.

• Remove any guards, covers, or hydraulic lines that obstruct access to the slewing drive assembly.

• Carefully disconnect all hydraulic hoses from the slewing motor. Be prepared to catch any residual oil and cap the lines and ports immediately to prevent contamination.

• Disconnect electrical connections to the swing brake sensor (if equipped).

• Unbolt and remove the slewing motor and reduction gearbox as an assembly.

2. Separating the Upper Structure:

• This is the most critical and dangerous part of the job. With the upper structure properly supported by stands, you will need to use a heavy-duty overhead crane or a large jacking system.

• Carefully lift the upper structure just high enough to clear the undercarriage and provide working space. Ensure it is stable and secure.

3. Removing the Old Slewing Bearing:

• Unbolt the slewing bearing from the upper structure and the undercarriage (swing circle).

• Due to its weight and often being corroded in place, removing the bearing can be challenging. Use threaded holes designed for "jack bolts" to push it out evenly. Avoid using excessive prying or hammering, which can damage the mounting surfaces.

4. Cleaning and Inspection:

• Thoroughly clean the mounting surfaces on both the upper frame and the undercarriage. Any old sealant, debris, or burrs will prevent the new bearing from sitting flush, leading to premature failure.

• Inspect the mounting bolt holes for damage and clean the threads.

5. Installing the New Slewing Drive:

• Apply a bead of recommended sealant to the mounting surface if specified by the OEM.

• Carefully lower the new or rebuilt slewing bearing into place. Guide it using alignment dowels or bolts to ensure it is perfectly centered.

• Install and tighten the new mounting bolts in the criss-cross pattern and to the exact torque values specified in the service manual. This is crucial for ensuring even clamping force and preventing distortion.

6. Reassembly:

• Reverse the disassembly steps.

• Lower the upper structure onto the undercarriage, guiding it onto the slewing bearing.

• Reinstall the slewing motor and gearbox assembly, connecting all hydraulic lines and electrical connections with new seals where needed.

• Fill the gearbox and hydraulic system with the correct type and amount of clean, new oil.

7. Testing and Final Checks:

• Reconnect the battery.

• Start the machine and operate the swing function slowly without load. Check for smooth operation and listen for unusual noises.

• Check for any hydraulic leaks around all new connections.

• Perform several full rotations in both directions to distribute the grease and oil.

A properly executed slewing drive replacement restores your excavator to full functionality and ensures safety and reliability for thousands of working hours to come. Always consult a professional if you are unsure about any step in this process.