Restoring the Ring Gear on a Massey Ferguson 300 Crawler Loader

[MikePhua]

The Massey Ferguson 300 and Its Mechanical Heritage
The Massey Ferguson 300 crawler loader was part of a generation of compact tracked machines built for utility, forestry, and light construction. Massey Ferguson, founded in 1953 through the merger of Massey-Harris and Ferguson, became a global force in agricultural and industrial equipment. The MF300 was powered by a Perkins diesel engine and featured a torque converter transmission with a wet sump configuration—making it distinct from clutch-type systems used in earlier models.
Though production numbers were modest compared to larger dozers and loaders, the MF300 earned a reputation for reliability and mechanical simplicity. Its compact frame and robust undercarriage made it ideal for tight job sites and rough terrain. Today, surviving units are often found in private fleets, restoration yards, and rural properties where they continue to serve as dependable workhorses.
Terminology Annotation
- Ring Gear: A circular gear mounted on the flywheel, engaged by the starter motor to crank the engine.
- Flywheel: A rotating disc attached to the engine crankshaft, storing rotational energy and supporting the ring gear.
- Wet Sump Torque Converter: A transmission system where the torque converter operates in an oil-filled housing, offering smoother power transfer.
- Flame Spraying: A thermal coating process used to build up metal surfaces by applying molten material.
- Knurling: A mechanical technique that creates textured patterns on metal surfaces to improve grip or fit.
The Ring Gear Fitment Challenge
A common issue in MF300 restoration involves sourcing a compatible ring gear for the flywheel. The original gear, designed for the wet sump torque converter configuration, is no longer manufactured. Replacement gears for clutch-type flywheels are readily available but differ slightly in internal diameter—resulting in a loose fit when installed on the torque converter flywheel.
In one case, a replacement gear was found to be approximately 0.050 inches too large, preventing a proper press fit. Attempts to reuse the old gear were ruled out due to severe tooth damage in two opposing spots, which caused the starter to disengage prematurely during cranking.
Proposed Solutions and Engineering Workarounds
To resolve the mismatch, several strategies were considered:

• Flame spraying the flywheel’s outer edge to build up material, followed by precision machining to achieve the correct interference fit.
  
• Knurling the flywheel surface using a chisel to create raised ridges, improving grip for the oversized gear.
  
• Welding the ring gear in place, though this was deemed risky due to potential imbalance and heat distortion.
  
• Custom machining a new ring gear from blank stock, which proved cost-prohibitive for a single unit.
  

Ultimately, flame spraying was selected as the most reliable method. This process involves applying a metal coating to the flywheel’s circumference, then turning it down to match the gear’s inner diameter. The result is a secure, serviceable fit that allows future replacement with standard clutch-type gears if needed.
Field Anecdotes and Practical Considerations
A technician in Missouri shared that he had reused a damaged ring gear by rotating it 45 degrees before reinstalling. Since engines tend to stop in predictable positions, this allowed the starter to engage fresh teeth. While clever, this method only works if the gear is minimally worn and removal was clean.
Another operator in Wisconsin recommended knurling the flywheel with a chisel, creating shallow grooves that grip the gear. He emphasized starting light and working evenly to avoid excessive tightness. Though effective in some cases, this method lacks the precision of flame spraying and may not hold under heavy use.
Preventative Measures and Long-Term Planning
To avoid future ring gear issues:

• Inspect starter alignment and engagement depth annually
  
• Replace worn gears before tooth damage spreads
  
• Maintain clean flywheel surfaces during installation
  
• Use Loctite or similar bonding agents only if recommended by the manufacturer
  
• Document gear dimensions and fitment methods for future reference
  

Operators restoring MF300 loaders should also consider sourcing spare gears while they remain available. Even if the fit isn’t perfect, having a donor gear on hand allows for machining or adaptation without delay.
Conclusion
Restoring the ring gear on a Massey Ferguson 300 crawler loader requires ingenuity and precision. With original parts no longer in production, adapting clutch-type gears through flame spraying or knurling offers a viable path forward. By understanding the mechanical nuances of the wet sump torque converter system and applying proven engineering techniques, owners can keep these classic machines running strong. In the world of vintage iron, every gear counts—and sometimes, the best solution is the one you build yourself.