Bobcat 763 Chaincase Removal and Drive System Maintenance

[MikePhua]

The Bobcat 763 and Its Mechanical Legacy
The Bobcat 763 skid steer loader was introduced in the late 1990s as part of the company’s push to modernize compact equipment with improved hydraulic performance and simplified serviceability. Powered by a Kubota V2203 diesel engine producing around 46 horsepower, the 763 became a staple in landscaping, construction, and agricultural fleets. With a rated operating capacity of 1,500 lbs and a vertical lift path, it offered a balance of reach, power, and maneuverability.
By the early 2000s, Bobcat had sold tens of thousands of 763 units globally. Its mechanical drive system, including the chaincase and drive chains, was designed for durability but required periodic inspection and service—especially in high-hour machines or those operating in abrasive environments.
Understanding the Chaincase and Drive System
The chaincase is a sealed compartment located beneath the operator’s cab, housing the drive chains that transfer power from the hydraulic motors to the sprockets. Each side of the machine has a pair of chains running over sprockets mounted to the axle shafts. These chains are submerged in gear oil, which lubricates and cools the moving components.
Terminology notes:

• Chaincase: A sealed housing containing drive chains and sprockets, responsible for transferring torque to the wheels.
  
• Drive chain: A heavy-duty roller chain that connects the hydraulic motor output to the axle sprockets.
  
• Sprocket: A toothed wheel that engages with the chain to transmit motion.
  

In Alberta, a contractor noticed his 763 pulling to one side. After inspection, one chain had snapped, and the chaincase oil was contaminated with metal debris.
Symptoms of Chaincase Wear or Failure
Operators may encounter the following signs of chaincase issues:

• Grinding or popping noises during travel
  
• Uneven drive response or steering drift
  
• Oil leaks beneath the cab or frame
  
• Excessive vibration or jerky movement
  
• Visible metal shavings in chaincase oil
  

If left unaddressed, chaincase failure can lead to:

• Loss of drive on one side
  
• Sprocket damage and axle misalignment
  
• Hydraulic motor strain
  
• Contaminated oil affecting other components
  

In Florida, a grading crew ignored a minor leak for weeks. Eventually, the chaincase ran dry, causing both chains to seize and requiring a full teardown.
Chaincase Removal Procedure
Removing the chaincase on a Bobcat 763 is labor-intensive but manageable with proper tools and preparation.
Step-by-step process:

• Park the machine on level ground and disconnect the battery
  
• Remove the operator cab by unbolting the pivot points and lifting with a hoist
  
• Drain chaincase oil using the bottom plug (capacity ~3 gallons)
  
• Disconnect hydraulic lines and mark their positions
  
• Unbolt the chaincase cover and remove with care
  
• Inspect chains, sprockets, and bearings for wear
  
• Replace damaged components and clean all mating surfaces
  
• Reinstall with fresh gaskets and torque bolts to spec
  
• Refill with SAE 90 gear oil and test drive system
  

Recommended tools:

• Hoist or overhead crane for cab removal
  
• Torque wrench rated to 150 ft-lbs
  
• Chain puller and breaker
  
• Oil catch pan and funnel
  
• Flashlight and inspection mirror
  

In Tennessee, a contractor added a magnetic drain plug to his chaincase. This helped monitor wear and catch early signs of sprocket degradation.
Preventive Maintenance and Long-Term Strategies
To extend chaincase life and avoid costly repairs:

• Change chaincase oil every 500 hours
  
• Inspect drive chains annually for stretch or corrosion
  
• Check sprocket alignment during tire changes
  
• Avoid aggressive turning under full load
  
• Use synthetic gear oil in cold climates to improve flow
  

Terminology notes:

• Chain stretch: The elongation of a roller chain due to wear, reducing engagement with the sprocket.
  
• Synthetic gear oil: A lubricant engineered for high-load and temperature stability, often with extended service intervals.
  

In Chile, a mining crew switched to synthetic oil and added a breather vent to reduce internal pressure. This eliminated recurring seal leaks and improved chain longevity.
Parts Availability and Sourcing Tips
Bobcat 763 chaincase components are available through:

• Authorized Bobcat dealers
  
• Aftermarket suppliers offering chains, sprockets, and seals
  
• Salvage yards with 700-series inventory
  
• Industrial chain manufacturers for custom replacements
  

Sourcing advice:

• Use serial number to match chain pitch and sprocket tooth count
  
• Cross-reference seals with NOK or Parker equivalents
  
• Seek hardened sprockets for abrasive soil conditions
  

In New Zealand, a contractor rebuilt his chaincase using industrial-grade chains from a conveyor supplier. The retrofit required minor machining but restored full drive function.
Operator Stories and Field Wisdom
In South Africa, a vineyard crew used a 763 for slope grading. After noticing steering lag, they discovered a loose sprocket inside the chaincase. Re-torquing the shaft bolts and replacing the lock washer resolved the issue.
In Poland, a snow-clearing team deployed a 763 for winter trail maintenance. After upgrading the chaincase seals and switching to cold-weather gear oil, the machine operated reliably through two harsh seasons.
Conclusion
The chaincase in a Bobcat 763 is a vital component that quietly powers every movement. When neglected, it can become a source of downtime and costly repairs. With disciplined maintenance, quality parts, and a clear understanding of its mechanics, operators can keep their machines running smoothly across all terrains. Whether grading gravel or pushing snow, the health of your chaincase determines the strength of your drive.