Troubleshooting the air systems on 8, 9, 10, 11, 13, 15, and 18-speed models is essential for maintaining smooth operation and preventing costly downtime. These transmissions rely on a precise air system to control shifting mechanisms, and understanding common problems—such as air leaks, low pressure, or component failures—can help identify solutions quickly. This Air System Troubleshooting Guide provides practical steps to diagnose and address air system issues, ensuring your Eaton Fuller transmission operates at its best.
Symptoms
- Air Leak at Shift Knob
- Air Leak at Slave Valve
- Air Leak from Transmission Breather or Transmission Case is Pressurized
- Air Leak at Splitter Cylinder Cover Exhaust Port
- No or Slow Range Shift into Low
- No or Slow Range Shift into High
- Range Shifts with Shift Lever in Gear
WARNING: Use care when removing air lines or checking for air flow from disconnected lines. High pressure air may exhaust suddenly. Wear safety glasses. Exhaust all air pressure from system before removing air filter/regulator or combination cylinder cover.
Note: During all testing, the vehicle air pressure must be greater than 90 PSI (620 kPa). If during testing the pressure falls below 90 PSI (620 kPa), make sure the transmission is in neutral, start the engine, and let the pressure build to governor cutoff. After the pressure reaches the governor cutoff, continue testing. The pressure is critical if the vehicle is equipped with a Pressure Protection Valve that would shut off the air supply to certain air circuits if the system pressure dropped below a preset level.
Air System Troubleshooting Procedures
Use the following air system troubleshooting procedures for part replacement only if the symptom can be duplicated. If the problem is intermittent, parts that are not defective could be replaced.
Instructions
- Start at “Procedures” for Step A.
- Based on the “Result” of the procedure, go to the corresponding “What To Do Next”.
Procedures
- Procedure 1: Symptom – Air Leak at Shift Knob
- Procedure 2: Symptom – Air Leak at Slave Valve
- Procedure 3: Symptom – Air Leak from Transmission Breather or Transmission Case is Pressurized
- Procedure 4: Symptom – Air Leak at Splitter Cylinder Cover Exhaust Port
- Procedure 5: Symptom – No or Slow Range Shift into Low
- Procedure 6: Symptom – No or Slow Range Shift into High
- Procedure 8: Symptom – Range Shifts with Shift Lever in Gear