Most brakes on the small tractors are on the right hand side of the transmission case. A few are on the left side. There is a disc and a brake block, and several pins and a wave washer. those types if not used a lot, or neglected, do tend to rust up and become inoperative. A good bath in PB Blaster penetrating liquid does wonders for making them work, although a complete dismantling of the brake assembly is usually needed to overcome the "Whoopee! NO BRAKES" condition! Rust and dirt are the main problems!
I'm not familiar with the JD type. If you have the tractor manual for your model, peer at it, and look for the place the brake operating rod goes back to the transmission. And, if you do take it apart, better take pics of it before dis-assembly! You will need to know!