Replacing a swing bearing on an excavator is one of the more complex maintenance jobs you can take on, and it requires careful preparation, proper tools, and strict attention to safety procedures. This is not a quick repair; it typically takes at least two full days for smaller operations, and even longer for larger machines or if complications arise. Rushing through the process can compromise safety or cause premature bearing failure, so it is important to move methodically. Below is a comprehensive guide to completing the job safely and correctly, and a process checklist for quick reference.
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Prepare Your Workspace
Before you begin, it is essential to set up the work area and gather everything you will need. Park the excavator on solid, level ground and ensure that the machine is properly secured so it cannot move during disassembly. The work zone should be roped off or marked to prevent unauthorized access while heavy lifting equipment is in use. Gather all the necessary tools, including lifting devices rated for the machine’s weight, new bolts, seals, silicone, and of course the replacement swing bearing. Always verify that the bearing’s part number matches your machine’s serial number, since even slight differences between models can result in improper fit or function. A mismatch here can waste time and money, or worse, create unsafe operating conditions once reassembled.
Step 1: Separating the Undercarriage from the Upper Structure
The first major step is separating the undercarriage from the machine’s upper structure. Begin by raising the entire machine carefully with appropriate lifting equipment, ensuring that the load is evenly supported. Ensure that the undercarriage is supported separately from the upper cab. Next, disconnect the rotary manifold and the existing swing bearing. All hydraulic lines should be capped, marked, and set aside in an orderly fashion to prevent contamination and to make reassembly smoother later on. Once the disconnections are complete, the undercarriage can be lowered back into place. This method, lifting the excavator upper structure slightly while leaving the undercarriage supported, is generally safer than attempting to hoist the entire cab away from the tracks. A more in depth explanation can be found here. Before moving forward, double-check that the machine is stable and securely positioned.
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Step 2: Removing the Old Swing Bearing
With the structures separated, the old bearing can be removed. Start by loosening and removing all the bolts securing it in place. Once unbolted, the bearing can be lifted out using lifting equipment. After removal, the turntable surface must be thoroughly cleaned of dirt, grease, and debris, as any residue can interfere with the seating of the new bearing. This is also the right time to carefully inspect the surface for damage such as cracks, pitting, or uneven wear. If the turntable surface shows significant damage, it may need repair or replacement before proceeding with the installation.
Step 3: Preparing the New Swing Bearing
A new swing bearing must be properly prepared before installation. Begin by cleaning it with brake cleaner and a clean rag to remove any excess oil used for shipping and storage. On DYCO bearings, look for the “S” stamp, which indicates the start and end of heat treatment. This area should be positioned in the section of the machine that experiences the least stress during operation, as it can be more vulnerable to fatigue. Once the orientation is correct, apply a thin, even layer of silicone to the turntable surface. This will help seal out dirt, moisture, and other contaminants that could compromise the new bearing over time.
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Step 4: Installing the New Bearing
Now the new bearing can be installed. Lower it carefully into position on the turntable, ensuring that the bolt holes are properly aligned. New bolts must always be used. Reusing old ones increases the risk of failure due to metal fatigue. Install the bolts and tighten them in a crisscross pattern, then torque each one to the exact specifications provided by the manufacturer. Following the torque sequence is critical to avoid uneven stress, which could distort the bearing. Once the bearing is bolted down, grease it thoroughly with a grease gun until grease begins to appear at the seals. This step helps ensure that the bearing is properly lubricated before it is placed under load.
Step 5: Reassembling the Excavator
The next step is carefully reuniting the excavator’s upper structure with its undercarriage. Slowly lower the upper frame onto the new bearing, taking extra care to align the swing gear. If the alignment is slightly off, you can use the machine’s hydraulics—made functional again by the capped lines—to make small adjustments until everything seats properly. Once aligned, secure the swing bearing to the cab using new bolts, again tightening them to the correct torque. Reinstall the rotary manifold with a new seal to prevent leaks, and reconnect all hydraulic lines, confirming that each one is correctly positioned and tightened. After all components are secured, the machine can be lowered completely and the lifting equipment removed.
Step 6: Performing Final Checks
Before declaring the job complete, a series of final checks must be performed. Inspect every connection, making sure all bolts are torqued correctly and that no lines or seals have been overlooked. Grease the swing bearing again to ensure proper lubrication. Once satisfied, start the machine and carefully check for any hydraulic leaks. Slowly test the swing motion to confirm smooth operation and correct alignment. Finally, conduct a thorough safety inspection of the entire work area and machine before returning it to service.
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Final Safety Notes
Throughout the process, safety should remain the highest priority. Replacing a swing bearing involves lifting heavy components, working with hydraulic systems, and handling precision parts, all of which carry risks if shortcuts are taken. Always work with a partner, and consult the OEM service manual for your specific machine model to confirm torque values, procedures, and part requirements. Using incorrect parts or skipping key steps may lead not only to premature bearing failure but also to potentially serious accidents. Taking the time to do the job correctly is the best way to protect both your investment and the people working around the machine.
For those who prefer a visual demonstration, additional help and a real-world example of a swing bearing replacement can be found on our YouTube channel.
Swing Bearing Process Checklist
- Park your excavator on a level surface
- Gather tools, lifting equipment, new bolts, seals, silicone, and the replacement swing bearing.
- Verify that the part number matches the part corresponding to your machine’s serial number.
- Raise the entire machine carefully using appropriate lifting equipment.
- Double check that both the upper cab and undercarriage are supported separately.
- Disconnect the rotary manifold and swing bearing.
- Cap and mark all hydraulic lines to prevent contamination and make reconnection easier.
- Lower the undercarriage back down.
- Secure the machine in place before continuing.
- Loosen and remove all bolts.
- Lift out the old swing bearing.
- Clean the turntable surface completely by removing all dirt, grease, and debris.
- Inspect the surface for cracks, wear, or other damage.
- Clean the new bearing with brake cleaner and a rag to remove excess oil.
- Look for the “S” stamp on DYCO bearings—this marks the start and end of heat treatment. Position this section where the bearing will experience the least stress.
- Apply a thin layer of silicone to the turntable surface to help seal out future dirt and grime.
- Position the bearing carefully on the turntable, aligning the bolt holes.
- Install new bolts (never reuse old ones).
- Grease the swing bearing with a grease gun until grease begins to seep out of the seals.
- Slowly lower the upper structure back onto the undercarriage, carefully aligning the swing gear. If misaligned, use the machine’s hydraulics (enabled by capped lines) to make fine adjustments.
- Secure the swing bearing to the cab with new bolts and torque them to spec.
- Reinstall the rotary manifold with a new seal.
- Reconnect all hydraulic lines.
- Lower the machine completely and remove lifting equipment.
- Inspect all connections and torque settings.
- Grease the swing bearing again as needed.
- Start the machine and check for hydraulic leaks.
- Test swing motion carefully to confirm proper alignment.
- Perform a final safety inspection before returning the machine to service.
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