Transmission Air Pressure Test. Diagnosis and Testing

Transmission Air Pressure Test

A hydraulic clutch problem can be located by a series of checks, replacing air pressure with fluid pressure to locate the concern.

1. Install the forward clutch and low/reverse clutch, connecting the main control to the transmission.

1. 1
   Using a rubber-tipped air gun, apply 40 psi (276 kPa) to the suspect clutch port for 2-3 seconds.
   

   • A thudding sound indicates clutch piston application.

   • A hissing sound may indicate leakage in the hydraulic circuit. Hydraulic circuits that use angled seals and/or air bleeds will have normal leakage.
2. 2
   Holding the air gun nozzle firmly against the transmission case opening, release the trigger.
3. 3
   Wait 1-2 seconds.
   

   • A hissing sound may indicate leakage in the hydraulic circuit. Hydraulic circuits that use angled seals and/or air bleeds will have normal leakage.
4. 4
   Remove the air gun from the port.
   

   • A sudden release of air pressure indicates that the hydraulic passages are able to hold pressure.

   • A lack of noise may indicate a leak in the hydraulic circuits. Some leakage is normal in hydraulic circuits that use angled seals and/or vent valves.