My 93 4WD Suburban (4L60E) will not shift into low or OD except when cold and usually forcing it to shift by manually moving the shift lever. I checked the voltage on all the solenoids at the computer and they all appear OK except the 3 to 2 downshift. I also shorted the solenoid pins to ground and they all "click" except the 3 to 2 downshift. Would this keep the tranny from shifting into low or OD? I am trying to figure out if I have a tranny problem or a computer problem????