Track Frame Misalignment on John Deere 850C Dozer Often Caused by Dry or Worn Pivot Shaft Bushings

[MikePhua]

John Deere 850C Dozer Background
The John Deere 850C crawler dozer was introduced in the late 1990s as part of Deere’s C-series lineup, designed for heavy-duty grading, land clearing, and site preparation. With an operating weight of approximately 45,000 pounds and powered by a 185-horsepower diesel engine, the 850C features a modular undercarriage, sealed and lubricated track chains, and a pivot shaft system that allows the track frames to oscillate independently. This design improves ground contact and traction on uneven terrain.
John Deere, founded in 1837, has long been a leader in construction and agricultural equipment. The 850C was widely adopted by contractors and municipalities for its balance of power, durability, and serviceability.
Symptoms of Track Frame Misalignment
A common issue with the 850C is track frame misalignment, where one side of the undercarriage appears to tilt outward at the bottom. This condition can cause:

• Uneven wear on the inside of the sprocket teeth
  
• Track chains jumping over roller flanges, especially when operating on side slopes
  
• Increased wear on bottom rollers and idlers
  
• Reduced track life and compromised stability
  

In one case, the left track frame was found to be ½ to ¾ inch farther out at the bottom than the right, despite equal clearance between the frames and the main body.
Root Cause and Mechanical Explanation
The most likely cause of this misalignment is a dry or worn pivot shaft bushing. The pivot shaft, also known as the dead axle, connects the track frames to the mainframe and allows limited oscillation. If the bushing inside the pivot housing wears out or loses lubrication, the affected track frame can sag or tilt outward.
This misalignment is not typically adjustable through shimming or bolt repositioning. Instead, it reflects internal wear that must be addressed mechanically.
Inspection and Repair Procedure
To confirm and correct the issue:

• Inspect the pivot shaft housing for signs of wear or dry grease fittings
  
• Check for movement by jacking up the dozer and prying the track frame outward—excess play indicates bushing wear
  
• Drain and refill the pivot shaft housing with the correct lubricant (typically SAE 140 gear oil or equivalent)
  
• Disassemble the pivot shaft if necessary to replace worn bushings or bearings
  
• Check bottom roller installation—ensure correct placement of single and double flange rollers, as incorrect configuration can exacerbate misalignment
  

In one field repair, a technician discovered the pivot shaft housing was completely dry. After replacing the bushing and refilling the housing, the track frame returned to proper alignment and the sprocket wear ceased.
Preventive Maintenance Recommendations
To avoid future misalignment:

• Grease pivot shaft fittings every 100 hours or as specified in the operator’s manual
  
• Inspect undercarriage components weekly for signs of uneven wear
  
• Replace worn rollers and idlers in matched pairs to maintain balance
  
• Monitor track tension and adjust according to terrain and usage
  
• Use high-quality lubricants to reduce internal wear in oscillating joints
  

Conclusion
Track frame misalignment on the John Deere 850C dozer is most often caused by dry or worn pivot shaft bushings. This condition leads to uneven sprocket wear and track instability, especially on slopes. By inspecting the pivot shaft housing, maintaining proper lubrication, and replacing worn components, operators can restore alignment and extend the life of the undercarriage. For machines operating in rugged terrain, regular undercarriage inspections are essential to prevent costly downtime and structural damage.