I assume you are talking about the master/slave cylinder system that activates your clutch. I don't know anything about JD, but if it is like a Ford tractor DO NOT use automotive brake fluid. CNH has a special oil for the brake system which is not trans/hydraulic oil or brake fluid. Anything else will deterioriate the soft parts of the system.
It might be that your JD requires brake fluid, but be certain before you add it. Possibly the filler cap/dipstick has the fluid requirements imprinted on it?
Ordinary brake fluid can pick up moisture from the atmosphere, maybe this is why there are certain specifations, Why don't you check out on Google? List the tractor model then something like specs, & fluids, see what you can come up with.
DOT 3 will work(what I've always used)...DOT 4 is better( if I remember correctly, its main advantage is it doesn't pick up moisture as readily as DOT 3). Wrong fluid...hydraulic or atf...will ruin soft parts...best to consult the book.