So I bought an old 660. It has always been a little slow going into reverse. As in you put it in reverse and rev it and you hear it chattering a bit then it will finally go into gear with a jolt. Today driving it around I started it and it wouldn't move forward. just a grinding noise. I put it in 4wd and it moved enough so I could park it. Any input on this is much appreciated because we need this to do maintenance on our property. Thanks guys!