Michigan 175G Torque Converter Failure and Hydraulic Drive Troubleshooting

[MikePhua]

The 175G and Michigan’s Wheel Loader Heritage
The Michigan 175G wheel loader was part of Clark Equipment’s heavy-duty lineup during the late 1970s and early 1980s. Built for quarry work, bulk material handling, and industrial loading, the 175G featured a robust frame, planetary axles, and a torque converter transmission designed for high tractive effort and smooth gear transitions. With an operating weight over 40,000 lbs and a bucket capacity exceeding 4.5 cubic yards, it was a staple in North American construction fleets.
Clark Equipment, founded in 1916, was a pioneer in mechanical drive systems and industrial loaders. The Michigan brand became synonymous with rugged simplicity and field serviceability. The 175G was powered by a Detroit Diesel 6V92 or Cummins NTC engine, depending on configuration, and paired with a Clark 28000 series transmission and single-stage torque converter.
Torque Converter Function and Failure Modes
The torque converter in the 175G serves as a fluid coupling between the engine and transmission. It multiplies torque during acceleration and allows smooth gear changes without clutch engagement. The converter consists of three main components:

• Impeller (driven by engine)
  
• Turbine (connected to transmission input)
  
• Stator (redirects fluid flow for torque multiplication)
  

Common failure symptoms include:

• Loss of drive in forward or reverse
  
• Sluggish acceleration or delayed engagement
  
• Overheating transmission fluid
  
• Metallic noise or vibration from converter housing
  
• Contaminated fluid with metal shavings or burnt odor
  

A technician in Alberta once diagnosed a 175G with intermittent forward movement. After pressure testing the converter circuit, he discovered a failed stator sprag clutch, which caused fluid recirculation without torque multiplication.
Hydraulic Drive Circuit and Pressure Testing
The 175G’s transmission relies on hydraulic pressure to engage clutches and modulate gear shifts. The torque converter shares fluid with the transmission sump and is cooled via an external oil cooler. Key components include:

• Transmission pump (gear or vane type)
  
• Converter charge circuit
  
• Pressure relief valves
  
• Directional control valves for forward/reverse
  
• Cooler bypass and filter housing
  

To diagnose converter issues:

• Install pressure gauges at converter inlet and outlet ports
  
• Measure charge pressure (typically 60–90 psi at idle)
  
• Check converter outlet temperature (should not exceed 220°F)
  
• Inspect filter for debris or blockage
  
• Verify directional valve response and solenoid function
  
• Perform stall test to assess torque multiplication under load
  

A restorer in Chile rebuilt his 175G’s converter after discovering low charge pressure and overheating. The root cause was a collapsed suction hose between the sump and pump, restricting fluid flow and starving the converter.
Rebuild Procedure and Component Sourcing
Rebuilding the torque converter requires precision and cleanliness. Recommended steps include:

• Drain fluid and remove converter housing from bellhousing
  
• Disassemble impeller, turbine, and stator assemblies
  
• Inspect sprag clutch, bearings, and sealing surfaces
  
• Replace worn components with OEM or matched aftermarket parts
  
• Clean all passages and reassemble using alignment tools
  
• Torque bolts to spec and verify clearance
  
• Flush transmission and refill with approved fluid (e.g., SAE 10W or ISO VG 46 hydraulic oil)
  

Common replacement parts:

• Stator sprag clutch
  
• Impeller hub seal
  
• Turbine shaft bearing
  
• Converter housing gasket
  
• Cooler bypass valve
  

A contractor in Texas rebuilt his converter using a remanufactured stator and upgraded seals. After installation, the loader regained full torque response and operated without overheating.
Preventive Maintenance and Long-Term Reliability
To extend converter life:

• Replace transmission fluid every 500 hours or annually
  
• Inspect suction hoses and clamps for collapse or leaks
  
• Clean cooler and filter housing during service intervals
  
• Monitor charge pressure and fluid temperature monthly
  
• Avoid aggressive gear changes under load
  
• Document rebuild history and part numbers for future reference
  

A fleet manager in Florida added converter pressure checks to his quarterly inspection protocol and reduced transmission failures by 50% across his Michigan loader fleet.
Conclusion and Recommendations
Torque converter failure in the Michigan 175G is often a result of fluid starvation, internal wear, or pressure imbalance. With methodical diagnostics, high-quality rebuilds, and disciplined maintenance, the machine can return to full operational strength.
Recommendations include:

• Pressure test converter circuit before disassembly
  
• Replace worn sprag clutches and seals with matched components
  
• Maintain clean fluid and inspect cooler flow regularly
  
• Document service intervals and rebuild procedures
  
• Train technicians in hydraulic diagnostics and converter teardown
  

With the right approach, the 175G continues to load, haul, and climb with the mechanical confidence that made Michigan loaders a cornerstone of industrial productivity.