Drott Cruz-Air 40 Troubleshooting and Mechanical Legacy

[MikePhua]

The Rise of Drott and the Cruz-Air Series
Drott Manufacturing Company, founded in the early 20th century and later acquired by Tenneco/Case in 1968, was known for its innovative approach to multipurpose excavators and wheel machines. The Cruz-Air series, including the Model 40, was designed to offer mobility and versatility in urban and highway environments where tracked excavators were impractical. These machines were widely adopted by municipalities and contractors for roadwork, utility trenching, and light demolition.
The Drott Cruz-Air 40, particularly the 40-YR variant produced in the late 1970s, featured a Detroit Diesel engine and a Reverse-O-Matic transmission. While exact production numbers are scarce, the Cruz-Air series saw widespread use across North America, with many units still operational decades later thanks to their robust mechanical design and field-repairable systems.
Core Features and Mechanical Layout
The Cruz-Air 40 was a wheeled excavator with a center-mounted boom and a rotating upper structure. Its drivetrain was powered by a Detroit Diesel 4-53 engine, delivering approximately 140 horsepower. The transmission was a Reverse-O-Matic unit, commonly used in compact cranes and rollers of the era.
Key specifications included:

• Operating weight: Approximately 28,000 lbs
  
• Boom reach: Around 20 feet
  
• Drive system: Air-actuated transmission with electric shift solenoids
  
• Swivel system: Triple-layered (air, electrical, hydraulic)
  
• Brake and throttle: Air-operated
  
• Outriggers: Manually controlled with mechanical linkages
  

The machine’s design prioritized modularity, with separate systems for propulsion, hydraulics, and electrical control. This made it easier to isolate faults but also introduced complexity in troubleshooting.
Terminology Clarification

• Reverse-O-Matic: A transmission system that uses electric solenoids to shift gears, common in mid-century industrial equipment.
  
• Swivel: A rotating joint that allows hydraulic, electrical, and pneumatic lines to pass between the upper and lower structures of the machine.
  
• Solenoid: An electromechanical device that actuates valves or switches using magnetic force.
  
• Outriggers: Extendable supports that stabilize the machine during digging or lifting operations.
  

Common Failures and Diagnostic Pathways
One of the most frequent issues with aging Cruz-Air 40s is failure to move despite the engine running smoothly. This typically stems from one of the following:

• Loss of air pressure to the transmission control valves
  
• Faulty or missing electrical signals to the shift solenoids
  
• Degraded swivel connections interrupting power or air flow
  
• Grounding issues in the wiring harness
  
• Manual safety interlocks not engaged
  

In one documented case, a Cruz-Air 40 sat idle for five years before being restarted. The engine ran well, and hydraulics responded, but the machine would not move. Inspection revealed capped-off air lines and a burned ground wire in the engine bay. After tracing the air system from the compressor to the cab, it became clear that a retrofit had been attempted but never completed. Reconnecting the air lines and repairing the ground restored partial function.
Field Repair Strategies
Operators and mechanics working on these machines often resort to creative solutions due to the scarcity of original parts. Recommended steps include:

• Use a multimeter or power probe to test solenoid function and continuity
  
• Inspect the swivel stack for corrosion, especially the electrical layer
  
• Replace missing or damaged air lines with DOT-rated nylon tubing
  
• Substitute obsolete solenoids with Trombetta units, modifying brackets as needed
  
• Install manual override switches in the engine compartment for starting and shifting
  

One technician in Manitoba recalled maintaining five Cruz-Air units for a municipal fleet. He noted that the pin clearance was intentionally undersized—2" pins were actually 1.990"—to reduce slop in the joints. This detail, unique to Drott, helped extend bushing life but required precision machining during rebuilds.
Operator Anecdotes and Lessons Learned
In Arkansas, a service tech remembered unloading a Cruz-Air 40 from a trailer with no brakes and only partial steering. The machine had a manual valve that reversed the steering wheel input for long-distance reverse driving—a feature rarely documented but invaluable in tight job sites.
Another operator in Wisconsin described the control system as a “rat’s nest,” with age-related degradation making troubleshooting difficult. He emphasized the importance of clean grounds and suggested installing a secondary start button in the engine bay to bypass unreliable dash switches.
Maintenance Recommendations
To keep a Cruz-Air 40 operational, consider the following:

• Test air pressure at the transmission control valve regularly
  
• Clean electrical swivels with brake cleaner to remove grease buildup
  
• Check solenoid resistance and replace units showing erratic behavior
  
• Grease all pivot points monthly, especially the boom and outrigger joints
  
• Inspect swivel seals annually and replace O-rings as needed
  

For machines stored long-term, it’s critical to purge moisture from air tanks and disconnect batteries to prevent corrosion.
Modern Comparisons and Legacy
Compared to today’s wheeled excavators like the Volvo EW series or Caterpillar M315, the Cruz-Air 40 lacks digital diagnostics, pilot controls, and emissions compliance. However, its mechanical simplicity and modular design make it ideal for restoration and use in low-tech environments.
While Drott no longer exists as an independent brand, its legacy lives on through Case Construction and the continued use of Cruz-Air machines in niche applications. The 40-YR model, with its Detroit power and Reverse-O-Matic transmission, remains a symbol of 1970s industrial ingenuity.
Conclusion
The Drott Cruz-Air 40 is a machine that rewards patience, mechanical intuition, and a willingness to adapt. Its layered control systems—air, electric, and hydraulic—can be daunting, but with the right tools and mindset, even a decades-old unit can be revived. For those who enjoy the challenge of vintage iron, the Cruz-Air 40 offers a rich blend of engineering history and hands-on problem solving.