Bobcat 843 Drive System: In-Depth Overview, Components, and Maintenance

[MikePhua]

The Bobcat 843 is a compact track loader known for its versatility and durability, with the drive system playing a crucial role in its overall performance. Understanding the design, components, common issues, and maintenance of the 843’s drive system helps operators ensure reliable and efficient operation.
Drive System Overview

• The drive system on the Bobcat 843 is a hydrostatic track drive setup.
  
• It uses hydraulic motors to power the rubber tracks, providing smooth, controllable traction.
  
• Designed for maneuverability in confined spaces and rough terrain, the hydrostatic drive allows variable speed control without shifting gears.
  

Key Components

• Hydraulic Pumps: Deliver pressurized fluid to the drive motors, usually driven by the engine via a power take-off shaft.
  
• Drive Motors: Convert hydraulic pressure into rotational motion to drive the sprockets attached to the tracks.
  
• Final Drive Assembly: Includes gears and bearings that transfer torque from the motor to the tracks.
  
• Track Chains and Rubber Tracks: Provide ground contact and traction; the chains support the rubber surface.
  
• Control Valves: Regulate hydraulic flow to enable precise speed and directional control.
  
• Hydraulic Reservoir: Stores fluid used by the drive system and cooling components to maintain optimal temperatures.
  

Terminology

• Hydrostatic Drive: A transmission system using hydraulic fluid to transmit power, enabling variable speed without mechanical gears.
  
• Final Drive: The last set of gears transmitting power to the track or wheel.
  
• Power Take-Off (PTO): A mechanism that transfers power from the engine to auxiliary systems like hydraulic pumps.
  
• Sprocket: A toothed wheel that engages with the track chain to move the track.
  

Common Issues and Diagnostics

• Track Slippage or Slow Movement: Often caused by low hydraulic fluid, worn drive motors, or track tension issues.
  
• Hydraulic Leaks: Leaks at motor seals, hoses, or fittings reduce pressure and efficiency.
  
• Unusual Noises: Grinding or whining may indicate bearing wear or gear damage in the final drive.
  
• Overheating: Prolonged heavy use without adequate cooling can degrade hydraulic fluid and components.
  

Maintenance Recommendations

• Hydraulic Fluid and Filter Changes: Replace fluid and filters every 500 hours or per manufacturer guidelines to maintain hydraulic system health.
  
• Track Inspection and Adjustment: Check track tension regularly; proper tension extends track and sprocket life.
  
• Seal and Hose Inspection: Look for leaks and wear; replace damaged seals or hoses promptly.
  
• Final Drive Lubrication: Ensure gear oil levels are adequate and change as scheduled.
  
• Cooling System Check: Keep hydraulic oil coolers clean to prevent overheating.
  

Operational Tips

• Avoid rapid direction changes to reduce strain on the drive motors and final drives.
  
• Operate the machine within recommended load and speed limits.
  
• Use the machine on suitable terrain to prevent excessive wear on tracks and drive components.
  
• Perform regular walk-around inspections for early detection of issues.
  

Case Example
An operator noticed a Bobcat 843 slowing down and exhibiting track slippage during work. Upon inspection, hydraulic fluid was low due to a small leak in a drive motor seal. After replacing the seal and refilling fluid, performance returned to normal, highlighting the importance of fluid checks and timely repairs.
Summary
The Bobcat 843 drive system’s hydrostatic design provides smooth, precise control ideal for various terrains and tasks. Proper maintenance of hydraulic components, tracks, and final drives is essential to ensure reliability and longevity. Early detection of leaks or unusual noises and adherence to operational best practices can prevent costly downtime.