alright, i just went through all of this. ive never had such poor luck with any of my I6s as i have had with this xj. (previously owned 2 amcs, both with the 4.2, basicly a carbed 4.0 with longer crank and a smaller bore) when i replaced my rear main seal, the first one was only a single lip. it leaked again. my second one was a double lip, but i found that my one piece oil pan gasket (awesome, but a pain to put in right) had actually came out of place around the rear main, cutting the corner of the U shaped piece that goes around it. the last time i did the rear main, i soaked the seal halves in oil for a couple days (was only supposed to be a couple of hours, but things got out of hand away from the jeep) then when i actually replaced the seal, had a friend hold the pan gasket up from the back corners, making sure the rear half loop of the pan gasket sat IN THE GROOVE. then i lifted the pan. all in all, with me doing all the work alone, took me 3.5 hours. not fun, but its like getting a shot. just say fuck it and do the damn thing. mines been leak free for a few days now, if it was gonna leak i think it would have by now. i took it out muddin the next day to celebrate. good luck