FDP15791 2004 with the auto shift transmission. It will not stay in 5th gear and will not stay in the higher reverse gears. It shifts through all gears even into 5th but drops within a second or two then acts like you switched into neutral as it reduces speed it shifts into 4th picks up speed goes into 5th then drops out again. Cat mechanic said they had a lot of the shifters go bad so I took it out and they said it tested bad. Put the new $840.00 shifter in and no difference. I also replaced the 5th gear lockout switch with no help. Does anyone have specs on speed sensor and the FWD high solenoid? Was thinking it may be one of them? Anyone had this problem. Everything else seems to works right. You can manually shift all gears as well as use the auto function just kicks out 5th Thanks for any help
Sucks not having info to diagnose it. I am sure it is out there just have to find it. Gotta be way to narrow it down but I bet it's gonna need hydraulic schematics and electrical to rule out the easy to access stuff before opening it up. Good luck, hope someone chimes in.
My feeling is it has to be electrical