How To Dismantle a Swing Gearbox

How To Dismantle a Swing Gearbox

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The swing gearbox on an excavator, paired with the swing motor and utilizing a slewing ring, allows the house of the excavator to swing freely of the excavator’s undercarriage and leads to one of the key traits of an excavator. But because of the consistent and heavy work they perform, swing gearboxes can be prone to wear and even failure, even under the best conditions.

If you’ve found yourself with a failing swing gearbox or you’re just interested in seeing inside of this interesting part, come along into one of the H&R Recon and Rebuild shops as an expert H&R parts technician disassembles a Komatsu PC360LC-10 excavator swing gearbox.



Dismantling a Swing Gearbox Process

  1. Remove the plug and drain the oil
  2. Remove the bolts from the ring gear.
  3. Lift off the ring gear and inspect the teeth for any wear or flaking.
    • In the above video, our parts technician, Matt, is working on a swing gearbox for a Komatsu PC360LC-10 excavator (a big excavator with a big swing gearbox) so he uses an overhead shop crane for help with the lift.
    • During inspection, pay close attention to any rounding of gear teeth or any flaking in the metal. Worn gear teeth will lead to inefficiencies in the gearbox and eventually larger problems so all worn parts should be replaced.
  4. Remove the carrier and separate the thrust washers and snap rings from the gears.
  5. You’ll now be able to remove the gears and inspect the bearings and surfaces of the carrier for wear. 
    • Notice how our parts technician uses both a visual and physical, hands-on inspection to ensure there is no unusual wear.
  6. Remove the sun gear and inspect it for wear. 
  7. Unbolt and remove the planetary carrier.
  8. Using a large punch, remove the planetary pins, bearings, and thrust washers, allowing the planetary gears to be removed.
  9. Inspect the splines and the bearings of the lower carrier.
  10. Tilt the gearbox to remove any leftover oil that has not drained.
    • Completely draining the oil will give you a clean look at the internals of the gearbox and a better surface to work with.
  11. The gearbox can now be flipped over and the bottom retainer plate unbolted.
  12. Using a press to evenly apply force, the pinion shaft should be forced free of the assembly.
    • In the video, you’ll notice that the pinion shaft doesn't come free initially using the press -- even though construction parts are designed for tough and demanding work, our parts technicians operate a press to never exceed certain values. In the video when the force of the press was too much, the H&R parts technician brought in the assistance of the H&R industrial parts oven to expand the parts and encourage their separation.
    • The heat from the oven will expand the steel 10 thousandths of an inch and decrease the friction of the combined parts. 
    • It might not seem like a big difference but the industrial parts oven is a key component in separating (and combining) parts without overapplying force to parts.
    • Once the entire assembly is heated the assembly is returned to the press and the press makes simple and quick work of separating the pinion shaft.
A gauge on a hydraulic press.
A handy gauge on this H&R press helps ensure parts are never subjected to too much pressure during the dismantling process. For this dismantle, the parts tech called in an assist from our industrial oven to help free the parts.
  1. Remove the upper bearings.
    • In the video, the parts technician calls in another tool to help with the process. This time, he uses a portable hydraulic ram to separate the bearing from the assembly.
  2. Remove the seal retainer, lower bearing, and pinion shaft using a hydraulic press.
    • It’s back to one of the presses for our parts tech to separate each component part from its shell.
    • In heavy construction equipment, parts are … well, heavy. Notice how the parts specialist uses assistive lift cranes, threaded eye bolts, and a forklift to help in moving each part.
    • In the video, you’ll see that once again, the press was unable to separate the parts. To ensure the parts aren’t damaged in the process, the technician relies on the industrial parts oven for an assist.
  3. Inspect the seal retainer plate, bearing, and all seal surfaces, checking for cracks and scratches.
  4. The swing gearbox should now be fully dismantled and all the parts ready for further inspection and preparation for a rebuild.

What’s the fate of the swing gearbox in the video?

After inspection, the upper and lower bearings were determined to be too worn to reuse for a rebuilt swing gearbox. As you can tell, disassembly was a detailed and often intricate process, but our parts technicians know that rebuilding a part with overworn parts only leads to issues down the road and they take pride in knowing the quality of their rebuilt parts is at the highest level. The fate of this particular gearbox will come down to the availability of replacement parts, cost, and market demand.


Whether you're on to your own gearbox dismantle and repair or you're just starting your research, as always, our Parts Specialist team is here to help connect you to a swing gearbox solution that will get you back up and running quickly.