My slip yoke is leaking in my 90 YJ. A friend told me that they will leak there if they are overfilled, but how can you overfill them through a 3/4 inch fill hole. Wouldn't the fluid just come out there? I think the rear seal is bad. Can someone lead me in the right direction and do I just pull off the rear housing? What is the NAPA part number for the seal? thanks guys.