Impossible to answer - would have to see it. How old is it and who owned it, if its a hay contractor then its prob tired out and bearings going.
Parts can be very expensive and not sure but think this is a very old model
Around here, you can buy them from $4500 - $7500. They are from the '80's and early '90's, and most are worn out. VERY expensive to repair, as is most JD equipment.
I recommend that you check the cost of repair parts on the piece before you buy it. We had a piece of older equipment break down last year during hay season and the nearest replacement part available was in Germany. Shipping parts to California from Germany is very expensive... if you were wondering.