Allis-Chalmers 840 Series – Rugged Classic, Inside and Out

[MikePhua]

The Allis-Chalmers 840, later followed by the 840B, represents a sturdy, mid-20th-century articulated loader that served many construction and industrial jobs. Though production wrapped up in the mid-1970s, its simplicity and power have earned it a loyal following in the restoration and vintage heavy-equipment community.
Technical Foundations

• The original 840 is driven by a Perkins 4-248 diesel engine producing approximately 74 net horsepower. It uses a torque converter mated to a three-speed forward/reverse transmission and planetary rear finals. Lift capacity lands around 9,000 pounds.
  
• The improved 840B swaps in a turbocharged Allis-Chalmers 2900 diesel, boosting flywheel horsepower to about 85 hp, while retaining the same drivetrain and planetary articulation architecture.
  
• Both models are detailed in a comprehensive parts catalog, featuring exploded diagrams and parts indices—for components ranging from hydraulics and steering to engine and electrical systems—ideal for maintenance or restoration projects.
  

Design Legacy & Historical Context

• Allis-Chalmers grew from multiple industrial firms into an expansive U.S. heavy-machinery maker spanning tractors, mills, mining, and more. Founded in the early 20th century, the company became known for robust, widely deployed equipment across sectors.
  
• The 840 loader fits within a lineage of heavy-duty machines, bridging earlier rugged models with successor Fiat-Allis loaders. Though no longer in modern production, many of these machines remain operational thanks to parts availability and a strong restoration community.
  

Use Cases & Anecdotes

• A midwestern farmer once acquired an 840B to replace a temperamental modern loader. Despite its age, the classic machine proved reliable—especially appreciated during a frozen spring, when faster, high-tech models struggled to start. The 840B’s simple mechanical systems and rugged build kept it moving under frigid conditions.
  
• Some operators report using refurbished units to handle heavy feed bags or silage, praising the loader’s steady lift and uncomplicated controls—even on uneven terrain.
  

Maintenance Tips & Practical Advice

• Prioritize bolt torque and wear points—articulated joints, bucket pins, and hydraulic linkage often bear the brunt of daily use.
  
• Clean and seal hydraulic connections regularly—aged rubber seals may crack, allowing fluid loss or contamination.
  
• Use the parts catalogs strategically—match up equipment serial numbers to ensure correct replacement parts, especially for engine, front-end, and hydraulic components.
  
• Upgrade with modern fluids—newer hydraulic oil or engine coolant can extend seal life and improve temperature handling without altering original parts.
  
• Consider weight-saving forks or buckets if lifting machinery is slow—lighter attachments ease strain on hydraulic systems.
  

Definitions & Glossary

• Torque Converter: A fluid coupling in the drivetrain that allows smooth transfer of engine power to the transmission, especially during load changes.
  
• Planetary Rear Finals: Heavy-duty gear systems providing torque multiplication and durability in the rear axles.
  
• Lift Capacity: The maximum weight a loader can raise safely—approximately 9,000 lbs in the 840 series.
  
• Flywheel Horsepower (hp): The engine’s output measure—not accounting for drivetrain losses—used to compare original and upgraded engine versions.
  

Quick-View Summary

• Engine Options:
  • Perkins 4-248 diesel ~74 hp
    
  • Allis-Chalmers 2900 turbo diesel ~85 hp (840B)
    
• Drivetrain:
  • Torque converter, 3-speed F-R transmission, planetary rear drive
    
• Lift Capability:
  • Around 9,000 lbs
    
• Maintenance Tools:
  • Parts catalogs with diagrams for precision servicing
    
• Advice:
  • Focus on hydraulic seals, articulation points, and matching parts via serial numbers
    
  • Use refreshed fluids to modernize performance subtly
    

Closing Thought
While the Allis-Chalmers 840 and 840B loaders may feel like throwbacks, their endurance and mechanical clarity continue to earn respect. With proper care, accurate parts, and basic upgrades, these orange workhorses can still thrive—and prove that solid engineering has a durability all its own.