i am looking at a buying a used B6200. Everything checked out good except that i could not shift it into 4WD. The linkage i believe is on the right side kind of under the seat. I could not budge the lever to move it forward which according to the tag should put it into 4WD. Is there anything special that needs to be done to engage the 4WD? The shift differential pedal seemes to lock in when depressed. Any one have any ideas about what could be wrong?