I have a 90 Sahara with the np231 transfer case. It has a 4" lift, 1 1/2" shackle, and a 3" body lift. My problem is, I am leaking fluid out of the center of the yoke behind the transfer case. I have replaced the rear oil seal and even put in a brand new yoke and it is leaking through the vent hole in the middle of the yoke and soaking the u joint. Any suggestions?