Clutch Test
ALLISON AUTOMATIC TRANSMISSIONClutch Test
Introduction Clutch test allows a technician to manually select each of the five forward ranges with the vehicle stopped. The intent of this procedure is to verify the ability of all five clutches to transmit torque without slipping.
Clutch Test Procedure
Use the Scan Tool to perform the clutch test. Select the following information when setting up the tool for running the test. Use the Shift Transmission feature on the Scan Tool to complete the clutch test.
1. Select-FO: Diagnostics and press ENTER.
2. Select-Model Year, i.e. 1 (20011.
3. Select-LDTrk, MPV, Incomplete.
4. Select-FO: Powertrain, press ENTER.
5. Select-Engine size, i.e. (G) 8.1L V8 L18 or (1) 6.6L V8 LB7 diesel, press ENTER.
6. Select-5 Speed Automatic, press ENTER.
7. Select-F2: Special Functions, press ENTER.
8. Select-F1: Transmission Output Controls.
9. Select-Shift transmission. This will allow the technician to shift the transmission and check the integrity of each clutch/range in the transmission.
Attach the transmission pressure gage. Apply parking brake and hold service brakes and increase engine speed to 1,400 RPM. With soft keys, select UPSHIFT and shift transmission from first gear range sequentially to fifth gear range, while observing turbine speed. Turbine speed should increase momentarily and then drop to 0 RPM when each gear range is attained. Line pressure should drop momentarily then regain pressure when each gear range is attained.
Maintain 1,400 RPM and select the DOWNSHIFT soft key and downshift transmission from fifth gear range sequentially to first gear range while observing turbine speed. Turbine speed should increase momentarily and then drop to 0 RPM when each gear range is attained.
To further investigate a suspected leak in a clutch circuit, the clutch test should be repeated keeping engine at idle speed. While performing clutch test at 600 RPM, main pressure should drop momentarily then regain pressure when each gear range is attained. If main pressure remains low, suspect damaged seal in that range. If low pressure is in first range only, suspect C5 piston seal damage.