System Pressure And Stall Speed, Check
System pressure/stall speed, check
Special tools:
999 2531 MANOMETER 999 2531 Manometer
999 5074 NIPPLE 999 5074 NIPPLE
Note! As the illustrations in this service information are used for different model years and / or models, some variation may occur. However, the essential information is always correct.
Oil level check
Check the oil level. See: Checking and adjusting the oil, AW55-50/51SN Checking Oil Level.
Ignition off
Manometer connection
Remove the air cleaner (ACL).
Remove the test plug from the transmission and fit nipple 999 5074 NIPPLE 999 5074 NIPPLE.
Connect the hose and manometer 999 2531 MANOMETER 999 2531 Manometer to the nipple.
Installing the air cleaner housing
Install the air cleaner housing with all hoses and electrical connections.
Idle speed check
Start the engine and allow it to idle with the selector lever in position N.
Check idle speed. See the table below.
System pressure check
Depress the brake pedal.
Move the selective levers to the various gears and read off system pressure.
Stall speed check
Check stall speed in conjunction with a system pressure check.
The check primarily provides information on the condition of the torque converter, transmission clutches and the engine.
Note! Never check stall speed if system pressure is low
The following is necessary to ensure correct test results:
- the engine provides full output
- system pressure is correct
- the transmission has the correct fluid level and operating temperature
Check
Air conditioning (AC) should be off. Place chocks behind all four wheels. Start the engine.
Caution! Apply the parking brake and depress the brake pedal hard with your left foot during the check.
Move the selector lever to D, apply full throttle max 5 seconds and read off the highest rpm as well as system pressure. Compare with the table below.
Note! The stall speed check must not last more than 5 seconds.
Repeat the check with the gear selector in R.
Compare with the table.
If the speed exceeds the table values, see High stall speed; if speed is below the table values, see Low stall speed.
High stall speed
Conditions of element Check above are fulfilled. Is the acceleration time for 0-100 km/h normal?
If the actual stall speed exceeds the normal value by more than 300 rpm:
Check if the oil is discolored or has a foul odor. See Checking and adjusting the oil, AW55-50/51SN Checking Oil Level.
If the oil is OK, replace the torque converter.
Replace the torque converter as described in Replacing the transmission, AW55-50/51SN Replacing The Transmission.
Dirty oil indicates worn or burnt clutch discs; replace the transmission.
Replace the transmission as described in Replacing the transmission, AW55-50/51SN Replacing The Transmission.
Low stall speed
Conditions of work element Check above are fulfilled.
If the actual stall speed falls below the normal value by more than 300 rpm, try a new torque converter.
Replace the torque converter as described in Replacing the transmission, AW55-50/51SN Replacing The Transmission.
Recheck stall speed after torque converter replacement.
If the fault remains, replace the transmission. See Replacing the transmission, AW55-50/51SN Replacing The Transmission replace (VCC-126316)
Finishing
After completion of the check:
Ignition off
Remove the air cleaner housing assembly with intake pipe.
Remove the manometer connection and the manometer.
Install:
- the test plug. Check that the O-ring is fault-free, replace as necessary. Tighten to 35 Nm
- the air cleaner housing with all hoses and electrical connections.