Diagnosing Power Loss in the Case W24B Loader

[MikePhua]

The Case W24B and Its Transmission Legacy
The Case W24B wheel loader was introduced in the late 1970s as part of Case Corporation’s push into mid-sized earthmoving equipment. Built for versatility in construction, agriculture, and municipal work, the W24B featured a robust frame, a six-cylinder diesel engine, and an Allison automatic transmission. Case, founded in 1842, had already established itself as a leader in agricultural machinery, and by the 1980s, its construction division was producing thousands of loaders annually. The W24B became a popular choice for operators who valued mechanical simplicity and reliability over electronic complexity.
The Allison transmission used in the W24B is a torque converter-based automatic system, designed to deliver smooth power transfer and minimal operator input. However, as these machines age, issues with hydraulic pressure, clutch engagement, and torque delivery can emerge—especially if maintenance intervals are skipped or components are exposed to contamination.
Symptoms of Power Loss in First Gear
Operators have reported that the W24B struggles to move from a standstill in first gear unless the engine is revved significantly. This behavior is most noticeable on flat terrain, where minimal resistance should allow easy movement. The engine itself runs smoothly, and higher gears engage with less hesitation, suggesting that the issue is isolated to low-speed torque delivery.
Terminology annotation:

• Torque Converter: A fluid coupling between the engine and transmission that multiplies torque at low speeds.
  
• Charge Pump: A hydraulic pump that supplies pressure to the transmission’s clutch packs and control circuits.
  
• Clutch Cutout Solenoid: An electrically actuated valve that disengages the transmission clutch under certain conditions, such as braking or idle.
  

Investigating the Charge Pump
The charge pump is a critical component in the Allison transmission. It maintains hydraulic pressure needed to engage clutch packs and shift gears. If the pump is worn, clogged, or leaking internally, pressure may drop below the threshold required to engage first gear effectively.
To test the charge pump:

• Install a pressure gauge at the transmission test port
  
• Measure pressure at idle and under load (typical range: 80–120 psi)
  
• Compare readings to factory specifications
  
• Inspect the pump housing for scoring or wear
  

If pressure is low, the pump may need to be rebuilt or replaced. In one documented case, a W24B with similar symptoms regained full functionality after the charge pump was replaced and the fluid flushed.
Clutch Cutout Solenoid as a Hidden Culprit
Another potential cause is the clutch cutout solenoid. This device disengages the transmission when the brake pedal is pressed or under specific idle conditions. If the solenoid is corroded, stuck, or receiving erratic signals, it may remain partially engaged—preventing full clutch engagement in first gear.
Recommendations:

• Locate the solenoid on the transmission housing
  
• Disconnect the electrical connector and test voltage during operation
  
• Manually actuate the solenoid to confirm movement
  
• Replace if resistance is outside spec or movement is restricted
  

A technician in Kansas reported resolving a similar issue by cleaning the solenoid terminals and replacing a frayed wire that was intermittently grounding the circuit.
Additional Checks and Preventative Measures
Beyond the charge pump and solenoid, other factors can contribute to sluggish movement:

• Low transmission fluid level or degraded fluid
  
• Clogged filters restricting hydraulic flow
  
• Worn clutch discs or seals inside the transmission
  
• Loose or misadjusted throttle linkage affecting engine response
  

Preventative maintenance tips:

• Change transmission fluid every 1,000 hours or annually
  
• Replace filters with OEM-grade components
  
• Inspect wiring harnesses for abrasion and corrosion
  
• Use infrared thermography to detect hot spots in the transmission housing
  

Field Anecdotes and Operator Experience
A contractor in Ontario shared that his W24B began exhibiting similar symptoms after sitting idle for six months. Upon startup, the loader hesitated in first gear and required high RPMs to move. After draining the fluid, replacing the charge pump, and cleaning the solenoid, the machine returned to normal operation. He now cycles the transmission monthly, even during off-season storage, to prevent valve sticking and fluid separation.
Conclusion
Power loss in first gear on the Case W24B is often a symptom of hydraulic pressure deficiency or electronic interference in clutch engagement. By methodically inspecting the charge pump, clutch cutout solenoid, and fluid condition, operators can restore full functionality without resorting to major transmission overhauls. In legacy machines like the W24B, understanding the interplay between mechanical and hydraulic systems is key to keeping them productive for decades to come.