Hi
I have just read this on the subject, which appears to match the symptoms on mine (I just need to work out how to identify what the vacuum modulator is now...
This section pertains to the vacuum modulator
Adjust the modulator only after you have verified the proper function of the double acting solenoid. The modulator tells the transmission when to shift and it determines the quality of shift. The modulator pressure should be set at around 4 Bar at idle with no vacuum line attached. This setting will give you a place to start, however, the modulator pressure should be set according to the operation of the car. Remember: Early and/or slip shift is low modulator pressure. Late and/or hard shift is high modulator pressure. These transmissions start in 2nd gear unless it starts off at full throttle, or the gear selector is in low. The fluid coupler (torque converter) makes the transmission feel like it is slightly slipping (750 RPM) until it quickly hooks up.
1) Remove the vacuum line from the modulator assembly on the transmission with the engine running. There should be at least 15 inches of vacuum at the line.
2) Check the modulator pressure at the test port to make sure you have around 4 bar at idle with no vacuum.
3) Install the vacuum line and drive the car. If it shifts too early, you need to raise the modulator pressure. You do this by loosening the lock nut on the small shaft in the center of the vacuum modulator. Turn this small shaft in (clockwise) 1/2 turn. Tighten the lock nut while holding the adjuster shaft in place. Repeat until the shift is correct. If the complaint is late or hard shift, follow the same procedure except turn the adjustment shaft out (counter clockwise) to lower the modulator pressure.
Some operational problems may be caused by valves in the valve body reacting slowly due to the bores being freshly honed. These symptoms will go away after a few days of driving.
Mark.
