Mine is a Husqvarna so I do not know if they are the same, or even close, but I will tell you how I got mine going.
I hope this makes sense, but here goes.
Pull the rear wheels off, and on mine the inside of the wheels are splined, to match a splined drive wheel also inside the wheel hub. Mine has a "C" clip holding the drive gear on. Pull the c clip and remove the drive gear, paying close attention to the order of parts.
Mine has a spring loaded pawl that engages the inside of a triangular opening, on the inside of the drive gear. Mine was simply crudded up inside. The little pawl is held in place by a fine wire spring, where one end of the spring hooks into a hole in a flat washer/spacer that the drive gear goes up against.
If the spring is broken, you'll have to replace it, otherwise clean it and inspect for wear or if it is bent and not operating as it should. A little studying will show you how it functions. Centrifugal force throws the pawl out to engage the triangular opening on the back of the drive gear.
Also, on mine, once all this is removed from the rear, there is another "C" clip, and behind that, there is a bearing that is a one way bearing (so they tell me). That got a little rusty on mine and I freed it up with some penetrating oil.
Hope this helps some, like I said, not sure what the JD's are like.
