Ditto on the geared starter. They are surprisingly affordable. You might spend less buying a geared starter than you will having your starter "check out". I'm guessing someone will at a minimum replace the brushes in your JD starter.

If you haven't already experienced it, you won't believe how fast a relatively small geared starter will turn over a diesel engine. Actually, the same with gas engines. Look at the factory starter on a new JD 500+ hp diesel. It's about the size of a can of pop.