Removing the 4-in-1 Bucket Cylinder on a CAT 943 Loader

[MikePhua]

The CAT 943 and Its Hydraulic Architecture
The Caterpillar 943 track loader was introduced in the mid-1980s as a compact yet powerful machine for grading, loading, and land clearing. With an operating weight of approximately 13,000 kg and powered by a CAT 3204 diesel engine producing around 90 horsepower, the 943 was designed to bridge the gap between smaller rubber-tired loaders and larger crawler units. One of its standout features was the optional 4-in-1 bucket, which added versatility for dozing, clamping, grading, and dumping.
The 4-in-1 bucket relies on a pair of hydraulic cylinders mounted to the bucket shell and frame. These cylinders control the clamshell motion, allowing the operator to grip logs, spread material, or dump with precision. Over time, these cylinders may leak, lose pressure, or suffer mechanical damage, requiring removal and rebuild.
Terminology Note

• 4-in-1 Bucket: A multi-function bucket with a hinged clamshell design operated by hydraulic cylinders.
  
• Cylinder Pin: A hardened steel pin that secures the cylinder to the frame or bucket.
  
• Gland Nut: A threaded collar that retains the rod seal and allows access to internal components.
  
• Pivot Boss: The reinforced area on the bucket or frame where the cylinder mounts.
  

Preparation and Safety Measures
Before removing the cylinder:

• Park the loader on level ground and lower the bucket
  
• Shut down the engine and relieve hydraulic pressure
  
• Disconnect the battery to prevent accidental activation
  
• Clean the cylinder area to remove dirt and debris
  
• Use blocking or cribbing to support the bucket if needed
  

Hydraulic fluid under pressure can cause serious injury. Always wear eye protection and use a rag when loosening fittings.
Cylinder Removal Procedure
The 4-in-1 bucket cylinders are mounted with two pins—one at the rod end and one at the base. Removal steps include:

• Disconnect hydraulic hoses from the cylinder ports and cap them to prevent contamination
  
• Remove retaining clips or bolts from the cylinder pins
  
• Use a drift and hammer or hydraulic press to drive out the pins
  
• Wiggle the cylinder free from the pivot bosses, using pry bars if necessary
  
• Inspect the mounting surfaces and pins for wear or scoring
  

In some cases, rust or paint buildup may bind the pins. Applying penetrating oil and gentle heat can ease removal. If the loader has been used in corrosive environments, expect resistance.
Anecdote from the Field
In 2022, a contractor in British Columbia removed both 4-in-1 cylinders from a CAT 943 after noticing uneven clamping and hydraulic fluid seepage. One pin was seized due to rust and required a custom puller fabricated from threaded rod and steel plate. After removal, the cylinders were rebuilt with new seals, polished rods, and fresh paint. The bucket regained full clamping force and operated smoothly for the remainder of the season.
Inspection and Rebuild Recommendations
Once removed, the cylinder should be inspected for:

• Rod straightness and chrome condition
  
• Seal integrity and gland nut wear
  
• Barrel scoring or pitting
  
• Bushing wear at the pivot ends
  

Rebuild kits typically include:

• Rod seal
  
• Wiper seal
  
• Piston seal
  
• O-rings and backup rings
  
• Gland nut
  

Use a seal installation tool and follow torque specs when reassembling. Pressure test the cylinder before reinstalling to confirm leak-free operation.
Manufacturer History and Loader Evolution
Caterpillar’s 943 was part of the 900-series track loader family, which included the 931, 941, and 953. The 943 offered improved operator comfort, better visibility, and enhanced hydraulic control compared to its predecessors. The 4-in-1 bucket option was especially popular in forestry and utility work, where material handling and grading were frequent.
Sales of the 943 peaked in the late 1980s, with thousands deployed across North America and Europe. Many units remain in service today, supported by a strong aftermarket for pins, seals, and hydraulic components.
Recommendations for Technicians and Operators

• Keep spare pins and seal kits in inventory for field repairs
  
• Lubricate pivot points monthly to prevent seizure
  
• Inspect cylinder rods for nicks or corrosion during routine service
  
• Replace both cylinders together to maintain balanced clamping
  
• Document removal and rebuild steps for future reference
  

Conclusion
Removing the 4-in-1 bucket cylinder on a CAT 943 loader is a straightforward but critical task in maintaining hydraulic performance. With proper preparation, safe handling, and attention to wear points, technicians can restore full bucket functionality and extend the life of this versatile machine. Whether gripping logs or grading soil, a healthy cylinder ensures precision and power where it counts.