Hello and thanks ahead of time to anyone who might be able to answer my question. I AM DESPERATE!! (Any help would be GREATLY appreciated) I am new to this forum and new to my 1988 diesel pusher. I have an Allison 4 speed transmission in this RV. One of the two button push button selectors which moves the trans down from R,N,D,3,2,1 works. The other button to move it back up does not work. I had the switch board and relay board out and tested. They found a bad diode and replaced it. It still does not work. This I am told works with a combination of electronics and air to work the solenoid by the transmission. I can move the gear shifter with my hands by the transmission easily. I must also mention that although the one button works, it was showing signs of having to push several times before changing the gears just as the other button did just before it stopped working all together. Any ideas what I need to look for to fix this problem? THANKS SO MUCH!