Identifying and Restoring a Vintage Skid Steer with a John Deere 4045D Engine

[MikePhua]

Uncovering the Identity of a Mislabeled Machine
A skid steer purchased at auction was initially believed to be a Bobcat S300, but its size and weight quickly raised doubts. The machine’s engine turned out to be a naturally aspirated John Deere 4045D—a 4.5-liter diesel not typically found in Bobcat models. With no legible serial badge and no frame stamp visible, the mystery deepened. The machine weighed approximately 10,000 to 12,000 pounds, far heavier than an S300, and its dimensions and lift capacity suggested a much larger class.
After careful inspection and community input, the machine was identified as a Melroe-Bobcat 975, a model produced from the mid-1970s through the early 1990s. The 975 was part of a lineage that began with the M970 in 1970, followed by the 974 (with a Perkins engine), and then the 975, which featured an 82-horsepower John Deere powerplant. The 975 was eventually succeeded by the 980, which introduced planetary drives but suffered from reliability issues.
Terminology and Component Notes
- Skid Steer Loader: A compact, rigid-frame machine with lift arms used for digging, grading, and material handling.
- 4045D Engine: A naturally aspirated 4.5-liter inline-four diesel engine produced by John Deere, known for reliability and torque.
- Serial Badge: A metal plate affixed to the frame that contains model and serial number information.
- Lift Cylinder: Hydraulic actuator responsible for raising and lowering the loader arms.
- Tilt Cylinder: Hydraulic actuator that controls the angle of the bucket or attachment.
Historical Context and Model Evolution
The Bobcat 975 was designed for heavy-duty applications, including tree spade operations, snow removal, and industrial loading. With a rated lift capacity of 3,700 pounds and actual lifting potential well beyond that, it became a favorite among contractors and municipalities. Its robust frame and high-flow hydraulics made it suitable for large attachments and demanding terrain.
The 975’s popularity stemmed from its simplicity and power. Unlike modern skid steers with electronic controls and emissions systems, the 975 relied on mechanical linkages and analog gauges. Its engine, the John Deere 4276 in earlier versions and later the 4045D, was known for long service life and easy rebuildability.
Restoration Strategy and Mechanical Assessment
The machine in question showed signs of hydraulic leakage from the right lift cylinder and left tilt cylinder—common wear points in older skid steers. The plan was to replace all cylinder seals and restore the hydraulic system to full function. The engine, despite its age, ran smoothly and started faster than newer trucks, indicating good compression and fuel delivery.
Recommended restoration steps:

• Remove and rebuild all hydraulic cylinders with new seal kits
  
• Inspect hoses for cracking and replace with high-pressure rated lines
  
• Flush hydraulic fluid and replace filters
  
• Clean and repaint the frame using industrial enamel or epoxy-based coatings
  
• Fabricate a new serial badge based on confirmed model identification
  
• Test lift and tilt functions under load to verify cylinder integrity
  

One technician noted that the 975’s hydraulic system was overbuilt for its time, allowing it to operate large snow buckets and tree spades without strain. A 9-foot snow bucket was a common attachment, and many units were retrofitted with auxiliary hydraulics for specialized tools.
Engine Identification and Replacement History
The presence of a 4045D engine raised questions about originality. While the 975 typically used the 4276, some units were retrofitted with the 4045D or even turbocharged variants. These swaps were often done during major overhauls or when original engines failed. The 4045D offers similar torque characteristics and fits within the same engine bay with minor bracket adjustments.
To verify engine history:

• Check casting numbers and block stamps for manufacturing date
  
• Contact John Deere with engine serial for production records
  
• Inspect mounting points and bellhousing for signs of modification
  
• Compare fuel system layout with original schematics
  

In one documented case, a contractor replaced a worn 4276 with a turbocharged 4045T to improve performance in cold climates. The swap required minor plumbing changes but resulted in better throttle response and fuel efficiency.
Preservation and Light-Duty Retirement
The new owner planned to retire the machine from heavy field use and assign it to carpentry shop duties—moving lumber, unloading equipment, and handling trailer loads. This light-duty role is ideal for older skid steers, reducing wear while preserving mechanical integrity.
Suggestions for long-term care:

• Store indoors or under cover to prevent rust and UV damage
  
• Run the engine weekly to maintain fuel system health
  
• Keep hydraulic fluid clean and monitor for leaks
  
• Use attachments within rated capacity to avoid frame stress
  
• Document all repairs and modifications for future reference
  

One restorer shared that his 975 had logged over 6,000 hours before being retired to a sawmill yard, where it continued to operate for another decade with minimal issues.
Conclusion
The rediscovery and restoration of a Bobcat 975 skid steer is a testament to mechanical resilience and the value of industrial heritage. With its John Deere engine, robust hydraulics, and heavy-duty frame, the 975 remains a capable machine even decades after production ceased. Whether hauling exotic lumber or clearing snow, its legacy endures—proof that good iron never dies, it just changes jobs.