Restoring a 1976 Case 780 Construction King Backhoe Loader

[MikePhua]

The Case 780 and Its Historical Role
The Case 780 Construction King was introduced in the mid-1970s as part of Case’s push to dominate the heavy-duty backhoe loader market. Built for demanding excavation, loading, and site prep tasks, the 780 featured a robust frame, high-capacity loader arms, and a powerful drivetrain. Case, founded in 1842, had already established itself as a leader in agricultural and construction machinery, and the 780 was a flagship model that helped solidify its reputation in the backhoe segment.
The 780 was powered by a Case diesel engine mated to a shuttle transmission, offering smooth directional changes and strong torque delivery. With its heavy loader bucket and deep digging backhoe, the machine was widely used in road building, utility trenching, and municipal work. Though production numbers were modest compared to later models, the 780 remains a respected workhorse among vintage equipment enthusiasts.
Initial Condition and Brake System Challenges
A recently acquired 1976 Case 780 was found to be in fair mechanical condition but suffered from complete brake failure. The brake system on this model can be configured with either air-assisted hydraulic master cylinders or a full air brake treadle valve. In some cases, previous owners bypassed the brake valve entirely, plugging the air line to avoid issues with sticking linkages.
Upon inspection, the master cylinders were found to be actuating when the treadle was pressed, but fluid levels were inconsistent—one side empty, the other full. Despite this, neither side produced braking force. The right wheel hub was coated in oil, suggesting a leaking seal that may have contaminated the brake drum. The parking brake, mounted behind the transmission, showed minimal stopping power and was also coated in oil, likely reducing friction.
Recommendations for brake restoration:

• Inspect and rebuild both master cylinders
  
• Replace contaminated brake shoes and clean drums
  
• Repair or replace leaking hub seals
  
• Bleed the system with assistance to ensure full actuation
  
• Consider replacing air lines and fittings if cut or degraded
  

Clutch Cutout and Shuttle Transmission Behavior
The Case 780 features a clutch cutout switch designed to interrupt power to the wheels when the brake is applied. In this unit, the switch was non-functional, and the air line leading to it had been cut, resulting in a loud hiss when activated. This suggests a failed or bypassed pneumatic control circuit.
The shuttle transmission relies on coordinated input from the clutch cutout and brake system to allow safe loader operation at high RPMs. Without proper disengagement, the machine may continue to drive forward even when braking—posing a safety risk.
Solutions:

• Trace and repair the air line to the clutch cutout valve
  
• Test the switch for continuity and air flow
  
• Confirm shuttle lever returns to neutral when braking
  
• Use the service manual to verify correct routing and valve function
  

Oil Leaks and Hub Maintenance
The right rear hub showed signs of significant oil leakage, coating the inside of the rim and likely contributing to brake contamination. This is a common issue in older machines where axle seals degrade over time. If left unaddressed, oil can saturate brake linings and reduce stopping power to near zero.
Steps for hub service:

• Remove the wheel and inspect the hub seal
  
• Replace the seal and clean the hub cavity
  
• Check bearing condition and preload
  
• Refill with appropriate gear oil and monitor for future leaks
  

In one case, a similar issue on a Case 580C led to complete brake failure during a downhill haul. After replacing the seal and shoes, braking performance was restored, and the operator added a routine hub inspection to his maintenance checklist.
Manuals and Documentation Access
For vintage machines like the 780, access to service manuals and parts catalogs is essential. Fortunately, digital PDFs and scanned documents are available through online marketplaces and CNH’s historical parts store. These resources provide exploded diagrams, hydraulic schematics, and torque specifications necessary for accurate repairs.
Suggested resources:

• CNH historical parts catalog for the 780CK
  
• Service manual for the Case diesel engine (DT series)
  
• Operator’s manual for shuttle transmission and brake system
  
• Wiring diagrams for clutch cutout and air brake circuits
  

Having these documents on hand allows owners to troubleshoot confidently and avoid guesswork—especially when dealing with mixed pneumatic and hydraulic systems.
A Story from the Field
In Montana, a new owner of a Case 780 described the machine as a major upgrade from his Ford 3500. Despite the brake issues, he was able to operate the loader and backhoe for several hours, noting the power and reach of the digging arm. After inspecting the brake system and confirming master cylinder actuation, he began sourcing parts and planning a full restoration. The machine had clearly seen hard use, but its core systems remained intact—a testament to Case’s engineering durability.
Conclusion
The Case 780 Construction King is a rugged and capable backhoe loader that, even decades after its release, continues to serve operators willing to invest in its upkeep. Brake system restoration, clutch cutout repair, and hub seal replacement are common tasks in reviving these machines. With proper documentation and a methodical approach, the 780 can be returned to reliable service. For those who appreciate mechanical simplicity and raw digging power, the 780 remains a worthy companion in the dirt.