One piece of advice use a dab of RTV on the bearing cap to create a seal between the top and bottom seal..Also make a wooden dowel to push the old upper seal out and the new in..Also get the best seal you can don't skimp...also make sure to use the proper torque on the rear cap... Like nick said don't bother till it's leaking like crap..drips are not worth it..The design of these rear mains are crappy, newer jeeps have been moved to a 1 piece design which seals much much better.