Evaluating the John Deere 690D LC Excavator Before Purchase

[MikePhua]

The 690D LC and Deere’s Excavator Transition Era
The John Deere 690D LC was part of Deere’s late-1980s push to establish a foothold in the hydraulic excavator market before its full transition to Hitachi-manufactured units. Built in the U.S. and powered by a robust diesel engine, the 690D LC featured a long undercarriage (LC) for improved stability and digging reach. With an operating weight around 47,000 pounds, a 3-foot rock bucket, and optional hydraulic thumb, it was designed for general excavation, demolition, and utility trenching.
This model marked the end of Deere’s in-house excavator production. Later models like the 690E and beyond were co-developed or fully built by Hitachi, reflecting a shift toward more refined hydraulics and electronic integration. The 690D LC, by contrast, retained a mechanical simplicity that appeals to operators seeking reliability over sophistication.
Terminology Annotation
- Swing bearing: A large-diameter bearing that allows the upper structure of the excavator to rotate on the undercarriage.
- Hydraulic thumb: An attachment mounted on the dipper arm that works with the bucket to grasp materials.
- Rails and rollers: Components of the undercarriage that guide and support the track chain.
- Final drives: Gear reduction units that transmit power from the hydraulic motors to the tracks.
Wear Indicators and Mechanical Red Flags
When evaluating a used 690D LC, several wear points deserve close attention. One seller noted that the swing bearing had noticeable play—described as something you could “feel.” This is a serious concern. Excessive movement in the swing bearing can lead to misalignment, structural fatigue, and eventual failure. Replacing it is neither simple nor cheap, often requiring disassembly of the upper frame and specialized lifting equipment.
Other reported issues included:

• Boom cylinders seeping hydraulic fluid
  
• Meter stuck at 8,800 hours, with estimated usage around 9,000
  
• One gallon of oil consumption per 100 hours
  
• New track rails and some roller replacements
  
• Cosmetic wear and uncertain maintenance history
  

While some seepage and oil consumption are expected in older machines, the combination of swing bearing wear and high hours suggests a unit nearing the end of its economic life.
The Risk of Misrepresented Equipment
A common frustration in the used equipment market is the discrepancy between seller claims and reality. One buyer contacted multiple sources about the same machine and received conflicting information. One seller claimed the machine didn’t use oil and had fully rebuilt cylinders, while another admitted to leaks and wear. This inconsistency highlights the importance of direct inspection and skepticism when dealing with brokers or “jockeys.”
Recommendations:

• Request detailed service records and ownership history
  
• Inspect the swing bearing for axial and radial play
  
• Check final drives for oil integrity—grease-filled units may indicate seal failure
  
• Verify hydraulic thumb operation and control valve condition
  
• Look for signs of fresh paint over worn components
  

A fresh paint job and new decals can mask serious mechanical issues. Always prioritize mechanical integrity over cosmetic appearance.
Hydraulic System Considerations
The 690D LC used Linde hydraulic components, which were known for performance but also for complexity and cost of repair. Later Deere-Hitachi models transitioned to more standardized systems. If the machine shows signs of sluggish response, erratic movement, or overheating, the hydraulic pump and control valves may be worn or contaminated.
Solutions:

• Perform a hydraulic flow test to assess pump output
  
• Inspect filters and fluid for metal particles or discoloration
  
• Replace worn hoses and check for internal delamination
  
• Consider retrofitting with modern hydraulic components if feasible
  

Hydraulic repairs on older machines can quickly exceed the value of the unit, especially if proprietary parts are involved.
Undercarriage and Structural Integrity
The undercarriage of the 690D LC is a major cost center. New rails and rollers are a positive sign, but the condition of the sprockets, idlers, and track pads must also be evaluated. Uneven wear or excessive slack can indicate frame distortion or improper tensioning.
Checklist:

• Measure track sag and adjust tension
  
• Inspect roller flanges for wear and cracking
  
• Check for weld repairs on the frame or boom
  
• Look for signs of structural fatigue near pivot points
  

A machine with a well-maintained undercarriage will perform better and cost less to operate over time.
Conclusion
The John Deere 690D LC represents a transitional moment in excavator design—mechanically rugged but nearing obsolescence in parts support and hydraulic refinement. When considering a purchase, especially one requiring a long trip, weigh the cost of repairs against the asking price. Swing bearing wear, hydraulic leaks, and inconsistent seller claims are red flags that warrant caution. For those seeking a reliable workhorse, better options may exist with lower hours and clearer histories. In the world of used iron, truth is the rarest commodity—and due diligence is the best defense.