Have a deutz agritron 150 and 4wd is always on ive changed solonide but still stuck on switch works as should with power on and off to the solonide. Any one any ideas ?
If the electrical part is OK, check is there play at the gearbox where the 4wd stub shaft is?
What can happen on those, is that the external 4wd shaft splines sieze and cause the internal 4wd shaft and supports to wear, which in turn looses oil pressure and leaves the 4wd permanently engaged.
Split and rebore bearing housing required in the worst case scenario.