Is it leaking around the throttle shaft and/or shutoff shaft? If so, it is just a few o-rings located in the top cover. Some say it can be done (carefully!) without removing the pump from the tractor, while others say it is easier to remove the pump. If you try it with it on the tractor, make sure the outside of the pump is absolutely clean, and pay attention to where the springs are connected to as you remove the top cover. I have one to do, but haven't decided which way to go. Since a loader frame is in the way, I'll probably remove the pump to be safe.