Initial Inspection and Diagnostic Overview

STALL SPEED

Do not conduct this test for longer than 5 seconds. Rear wheels must not be permitted to turn. Also, engine must be operating temperature and full power available. Turn all accessories OFF when conducting this test.
1. Connect a suitable tachometer onto engine as per manufacturer's instructions.
2. Start and operate engine at approximately 2000 RPM for 2 minutes prior to testing stall speed.
3. Apply parking brake completely and depress brake pedal.
4. Position selector lever into drive, completely depress accelerator pedal and check stall speed.
5. Stall speed obtained should be 2200-2600 RPM.
6. If stall speed drops by approximately 400-700 RPM, torque converter one-way clutch is slipping.
7. If stall speed exceeds specified limit by approximately 300 RPM, the transaxle is slipping.
8. If stall speed is correct and top speed is still not reached, one-way clutch is locking up in both directions or has seized. This will be noticed during fast highway driving by automatic transaxle fluid leaking through vent.
9. Stall speed will drop approximately 125 RPM for every 3280 ft. above sea level.
10. Excessively high ambient temperatures will affect stall speed.

MODULATING PRESSURE

The modulating pressure must be checked and, if necessary, adjusted before measuring any other pressure. Incorrect modulating pressure will adversely affect the operating pressure.
1. Disconnect vacuum line and plug opening, then accelerate vehicle on a dynamometer or road to 30 mph with selector lever in drive position and note pressure obtained.
2. Pressure readings should be 63.8 psi on A28.01 units, and 58 psi on A28.02 units. If pressure obtained is incorrect, proceed as follows:

a. Remove rubber cap from vacuum modulator.
b. Pull lock plate out slightly and turn vacuum modulator adjusting screw using the lock plate. One complete turn of adjusting screw will change modulating pressure by approximately 5.8 psi.
c. After adjustment lock plate must be pressed into nearest locking slot.

OPERATING PRESSURE

Operating pressure is not adjustable, modulating pressure automatically affects operating pressure. Pressure readings should be 245 psi on A28.01 units and 221 psi on A28.02 units.

GOVERNOR PRESSURE

When checking governor pressure, disconnect vacuum line. Governor pressure is part of the operating pressure and is brought to the necessary value by the centrifugal governor. Since governor pressure is derived from the operating pressure, operating pressure must be checked simultaneously. Operate vehicle on a dynamometer or the road and compare governor pressure with pressure readings listed. If no or deviating governor pressure is measured, the governor must be disassembled, cleaned and repaired.

CONTROL PRESSURE

Control pressure is part of the modulating pressure. It is regulated mechanically depending on position of the accelerator pedal. If modulating pressure is adjusted correctly, the control pressure will automatically be correct.