Removing the Recoil Spring on the John Deere 850C Dozer

[MikePhua]

The 850C and Its Undercarriage Design
The John Deere 850C crawler dozer was introduced in the late 1990s as part of Deere’s push into electronically controlled hydrostatic machines. With an operating weight of roughly 42,000 lbs and powered by a 6-cylinder turbocharged diesel engine producing around 185 horsepower, the 850C was built for heavy grading, site prep, and forestry work. Its undercarriage features a sealed and lubricated track system with a recoil spring assembly designed to absorb shock loads and maintain track tension.
The recoil spring is housed within the track frame and works in conjunction with the track adjuster cylinder. It compresses under load to cushion impacts from rocks, stumps, and uneven terrain, preventing damage to the track frame and final drives.
Purpose and Risks of Recoil Spring Removal
Removing the recoil spring is necessary when:

• The spring is broken or fatigued
  
• The track adjuster cylinder is leaking or seized
  
• The recoil assembly is binding or misaligned
  
• The track tension cannot be maintained
  

However, the recoil spring is under extreme compression—often exceeding 20,000 lbs of force. Improper removal can result in serious injury or equipment damage. A technician in Montana once attempted removal without proper jacking and the spring released violently, damaging the shop floor and narrowly missing a coworker.
Preparation and Safety Protocols
Before beginning:

• Park the machine on level ground
  
• Block the tracks and engage the parking brake
  
• Release track tension by bleeding the adjuster cylinder
  
• Use heavy-duty cribbing to support the track frame
  
• Wear eye protection, gloves, and steel-toe boots
  
• Use a hydraulic press or threaded compression tool rated for recoil springs
  

Never attempt removal with hand tools alone. The stored energy in the spring can eject components with lethal force.
Disassembly Sequence and Component Access
To remove the recoil spring:

• Remove track pads and loosen track chain
  
• Disconnect the grease fitting and bleed adjuster cylinder
  
• Unbolt the track adjuster housing from the recoil tube
  
• Use a compression tool to preload the spring
  
• Remove retaining bolts and slowly release spring tension
  
• Extract the spring and inspect for cracks or deformation
  
• Clean the recoil tube and inspect for scoring or rust
  

If the spring is broken, it may be jammed inside the tube. Use a slide hammer or hydraulic pusher to extract fragments. Replace all seals and bushings during reassembly.
Inspection and Replacement Guidelines
Check for:

• Spring length and coil spacing
  
• Surface cracks or corrosion
  
• Tube wear or ovality
  
• Cylinder rod straightness
  
• Seal integrity and grease passage clearance
  

Replace the spring if:

• It is shorter than spec by more than 5%
  
• Coils are uneven or collapsed
  
• Surface pitting exceeds 1 mm depth
  
• It has been overheated or discolored
  

Use OEM or equivalent high-tensile steel springs. Torque all bolts to factory spec and apply anti-seize to threads exposed to moisture.
Reassembly and Track Tensioning
To reinstall:

• Insert new spring and preload with compression tool
  
• Reattach adjuster cylinder and torque bolts
  
• Fill grease chamber and pump until track tension is achieved
  
• Reinstall track pads and verify alignment
  
• Test machine under light load and monitor tension
  

Track sag should be 1–2 inches at midpoint between rollers. Over-tensioning can cause premature wear; under-tensioning can lead to derailment.
Preventive Maintenance and Long-Term Reliability
To extend recoil spring life:

• Inspect track tension weekly
  
• Clean grease fittings and apply fresh lubricant monthly
  
• Avoid high-speed travel over rocky terrain
  
• Replace seals every 2,000 hours or during undercarriage rebuild
  
• Monitor spring housing for rust or impact damage
  

A contractor in Georgia added a drain plug to the recoil tube to prevent water accumulation. After three years, the spring showed no signs of corrosion and maintained full tension.
Conclusion
Removing the recoil spring on a John Deere 850C dozer is a high-risk but necessary procedure when track tensioning fails or the spring fatigues. With proper tools, safety protocols, and methodical disassembly, technicians can restore undercarriage integrity and prevent costly downtime. The recoil spring may be hidden beneath steel and grease, but its role in absorbing shock and maintaining track alignment is vital to the machine’s performance in harsh terrain.