Tractor Repair: Case 5140 powershift, pressure switch, solenoids

Question
Hello,
I have a 1990 Case 5140 mfd with 4000hrs. This tractor has a powershift with shuttle reverser. My problem is that I have only the 4th powershift gear in each of the 4 ranges. All the other powershift gears (1-3) went out at the same time. Could it be the shifter itself, shift solenoids, or is there a controller in the system?

Thanks for your help !!

Answer
  If all the other speeds quit working at the same time, it is most likely a bad pressure switch on the powershift control valve.  If you shift it to any of the speeds that don't work, a yellow light on the left side of the dash should come on.  Hold the clutch pedal down and count how many times the light flashes.  The controller flashes the light for an error code to help lead you to the problem, although I can't find my cheat sheet at the moment that tells what the number of flashes mean.  But I know that if the pressure switch for 4th powershift is stuck closed, that would be the only speed that works.  If you still can't figure it out, let me know how many times the light flashes and I will have to look it up to see what it means.