I have a Case 621B xt loader that will not move in the forward or reverse direction in 1st or 2nd gear. The machine will move normally in 3rd and 4th gears. We farm so the loader is not used on a daily basis. The machine was parked in the shed with everything working perfectly. Its has a leaking brake line in the front that we have not had time to repair. While setting in the shed some hydraulic fluid was lost, but the fluid was brought back up to the full level before starting the machine. Do not know if the low fluid level had anything to do with the issue. Trying the find a starting place for troubleshooting
Think I would first check the ohms reading on the shift solenoids on the trans control valve . Have had several go bad on our Hyundai loader with ZF transmission .
Could be the FNR switch also