We have a John Deere 644H payloader that we are having issues with. The loader will not shift out of second gear, Trans oil is good, New trans filter, we also swapped out what we believe is the trans speed sensor. Also note we have no speedo reading also. There are three screw in type sensors on the top of the trans that we believe are good. Checked continuity on all the wires back to the twist lock plug and they are check out good. Could it possibly be the FNR switch? It tries to shift into third when selected, but reverts back to 2nd gear after it studders for a moment.
I believe you still have an issue with the speed sensor circuit. What is the machine serial number? Press the menu button until the letter "d" with a "1" below it is displayed. Press select. What codes are listed? You will have to use the next button to see all the codes.
Machine serial number is DW644HX574478, and for whatever reason the buttons on the dash arent working, and it wont let me get into the codes.
Check fuse F23.
F23 is good.
I retract that statement,F23 is bad, was looking at wrong fuse. It blows as soon as you put new fuse in.
That is why you cannot shift out of first. On your serial number machine, that fuse supplies the voltage to the output shaft speed sensor. That fue also supplies voltage to some other items, so your short could be any one of those items or the wiring to them. I sent you the pertinent schematic that the F23 fuse supplies. Check your messages.
Thank you, that was very helpful. I ended up finding a shorted out wire by the rear taillights. My power probe short finder came in handy, as all the wires are bunched together in a loom.
These threads are the reason HEF exists. Success stories. Thank you @mg2361 for helping out, and @Johnson43 for reporting back.
I don't have one but several people have commented a power probe is fantastic diagnostic tool.