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Calibrating COMPUSHIFT Pro A750 N to D Engagement

Harsh neutral to drive engagement can be caused by three different things:

  • Incorrect clutch fill / stroke pressure (Problem A)
  • Incorrect clutch apply pressure (Problem B)
  • Incorrect clutch regulator settings (Problem C)
  • Some other transmission problem (Problem D)

Below is a procedure for determining the root cause of harsh N-D engagement, and making adjustments based on that determination.  This procedure presumes you are in a vehicle equipped with a CS3 connected to a Toyota A750 transmission.

Test Procedure

  1. Place the vehicle in neutral or park, and turn on the vehicle power / ignition switch and start the engine.
  2. Connect with to the CS3 with the CS Setup app.
  3. Back up the CS3 configuration by using "Save to File" from the top menu.
  4. Navigate to the Shift Control Setup / Advanced Menu.
  5. Set these parameters as follows, taking note and reporting their value before adjustment..
    1. Torque Shift I Constant → 0
    2. Torque Shift P Constant → 0
    3. Torque Shift D Constant → 0
    4. N-1 Shift Pressure at 0% torque → 0   
  6. With a foot gently on the brake pedal, move the shift lever from N-D and observe if any engagement occurs. If engagement occurs momentarily, then you have Problem A and you can go to "After Testing".  You can move the lever from N-D / D-N a few times to see if engagement starts to happen.  If not, continue testing.
  7. Navigate to the Shift Control Setup / Advanced Menu / N-1 Shift Pressure.
  8. Select the pressure for 0% torque (which should still be 0).
  9. With a foot gently on the brake pedal, move the shift lever from N-D.  No engagement should occur. 
  10. Progessively increase the 0% engagement pressure by 10 kPA at a time until engagement occurs.  It's easiest to release on the brake pedal (while keeping your foot on it), as you increase the pressure, as the vehicle will start to move forward when engagement occurs.  Be sure to be ready for the vehicle to move.  Note the pressure where engagement occurs.  If engagement does not occur, after about 300 to 400 kPA, you have some other problem (Problem D).  Note this pressure and go to "After Testing".  
  11. Move the shift lever from N-D, keeping your foot on the brake.  Based on the calibration in step 10, you should have smooth engagement now.  Note and confirm this fact.  If this pressure is close to the original pressure noted in step 5, then you have Problem C.  If not, you have Problem B.

After Testing

After testing, you can reload the original values for the items set in 5 a,b,c,d or you can restore the values using the backup you made in step 3.

Report back all pressures and problems.  If you have problem A, you can try reducing Clutch 1 stroke pressure by 20 kPA steps until you get smooth engagement.  Note that you can always revert to the backup you step in step 3.

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