I've replaced several Jeep 4.0L rear main seals over the years. It isn't a great design to begin with. I replaced the one in my Wrangler about 2 years ago. It was leaking enough where it was dripping on the ground, and coating the transmission and skid plate while driving. I could see a slight groove in the crank from the seal. When I replaced it, the leak was 90% fixed, but still weeped a tiny bit where it was wet around that area. I figured it was due to the groove I saw in the crank, and was happy that the leak was mostly fixed.
Oddly enough, I ran Maxlife synthetic 5w30 and after 3000 miles or so I went under the Jeep for something else and noticed the RMS was completely dry, no weeping at all, so I've just continued to run that oil and everything seems dry so far.
Oddly enough, I ran Maxlife synthetic 5w30 and after 3000 miles or so I went under the Jeep for something else and noticed the RMS was completely dry, no weeping at all, so I've just continued to run that oil and everything seems dry so far.