Restoring and Maintaining the Michigan 85GM-3A Wheel Loader

[MikePhua]

The Rise and Retirement of the Michigan 85GM-3A
The Michigan 85GM-3A wheel loader was part of a transitional era in heavy equipment manufacturing, produced under the Clark Equipment Company’s Michigan brand. Clark, founded in 1903 in Buchanan, Michigan, was a pioneer in material handling and earthmoving machinery. By the 1960s and 70s, Michigan-branded loaders were widely used in mining, construction, and municipal operations across North America.
The 85GM-3A was designed as a mid-range loader, positioned between the smaller 75 series and the larger 125 series. Its production was eventually phased out due to overlapping capabilities with adjacent models. Clark streamlined its lineup by upgrading the 75B and simplifying the 125B, effectively retiring the 85 series not for performance issues but for marketing efficiency. Despite this, the 85GM-3A earned a reputation for rugged reliability and is still found working on private properties and small operations today.
Engine and Powertrain Overview
The 85GM-3A typically came equipped with a Detroit Diesel 6V53N engine—a two-stroke, V6 diesel known for its high-revving nature and compact design. The 6V53N delivers around 200 horsepower and was widely used in military vehicles, buses, and industrial equipment. Its simplicity and parts availability make it a favorite among restorers, though it demands specific maintenance practices.
Key engine features:

• Two-stroke cycle with blower-assisted scavenging
  
• SAE 40 monograde oil requirement with low sulfated ash content (<1.0%)
  
• Emergency air shutoff system recommended to prevent diesel runaway
  
• High sensitivity to oil type—multi-grade oils like 15W-40 can accelerate wear
  

In Florida, an owner discovered his loader running beautifully after a basic oil and filter change, but later learned that Delo 400 exceeded the ash content threshold for the 6V53N. He switched to Delo 100 SAE 40, specially formulated for two-stroke Detroits, and noted improved oil consumption and smoother starts.
Transmission and Torque Converter Maintenance
The Michigan 85GM-3A uses a Clark 2420 transmission paired with a torque converter. This setup is known for its durability but requires careful fluid management and shifting discipline.
Maintenance recommendations:

• Use SAE 30 engine oil or Dexron (not Dexron II) for transmission fluid
  
• Drain both transmission and converter via the transmission sump plug
  
• Clean the suction screen behind the drain plug to check for metal debris
  
• Inspect and clean the converter cooler line strainer every 250 hours
  
• Avoid shifting between forward and reverse without a full stop to prevent gear damage
  

One operator found only 2.5 gallons of fluid during a drain, far below the expected 7-gallon capacity. After cleaning the screens and breathers, he refilled gradually, checking levels with the engine running and transmission in neutral. Overfilling risks foaming, which can lead to erratic shifting and gear wear.
Hydraulic System and Fluid Choices
Hydraulic fluid selection depends heavily on ambient temperature. For warm climates like Florida, AW 46 hydraulic oil is suitable. In colder regions, SAE 10 or 20 weight engine oil may be used.
Hydraulic system tips:

• Avoid multi-grade oils to prevent viscosity breakdown
  
• Change hydraulic filters regularly, even if fluid appears clean
  
• Inspect hoses for internal delamination—rubber fragments in screens signal failure
  
• Use sintered bronze breathers with check valves to prevent vacuum lock and oil blowout
  

In Georgia, a retired operator noted that some breathers lacked check valves, leading to oil spray and false alarms. Replacing or cleaning these breathers restored normal operation.
Cooling System and Antifreeze Selection
The Detroit 6V53N engine originally recommended Nalcool coolant, a specialized formula with corrosion inhibitors. However, many older machines ran reliably on standard automotive antifreeze before Nalcool became common.
Coolant guidelines:

• Use a 50/50 mix of ethylene glycol and distilled water
  
• Flush radiator before refilling to remove sediment and scale
  
• Check for leaks around hose clamps and water pump seals
  
• Monitor coolant level and temperature during initial startup after service
  

A technician in Ontario reported that switching from Nalcool to conventional antifreeze had no adverse effects, provided the system was flushed and maintained properly.
Breathers and Transmission Ventilation
Breather caps on the transmission and torque converter allow filtered air exchange, preventing pressure buildup and vacuum formation. These caps often contain small filters and check valves.
Servicing breathers:

• Remove and clean with solvent; inspect for missing or damaged check valves
  
• Replace sintered bronze filters only if clogged or cracked
  
• Identify breather locations—some may be hidden or replaced with non-standard fittings
  
• Consider installing extension nipples for easier access in tight compartments
  

One loader had a breather mounted on the control valve assembly, which was nearly inaccessible. The owner added a threaded extension to relocate the breather for easier maintenance.
Final Thoughts on Ownership and Restoration
Restoring a Michigan 85GM-3A is a rewarding endeavor for mechanically inclined owners. While parts can be sourced from suppliers like MinnPar and Allied Equipment, technical documentation may be scarce. Owners often rely on scanned manuals, peer advice, and hands-on inspection.
Checklist for new owners:

• Drain and replace engine, transmission, and hydraulic fluids
  
• Clean all screens, strainers, and breathers
  
• Inspect hoses, filters, and gaskets for age-related wear
  
• Verify emergency shutoff systems and fire suppression readiness
  
• Gradually refill fluids and monitor levels during warm-up cycles
  

Despite its age, the Michigan 85GM-3A remains a capable and dependable machine. With proper care and attention to its unique systems, it can continue serving for decades—proof that good engineering never truly goes out of style.