clsnidahoredneck

Sorry in advance for the long story, but I'm hoping the more details, the better. So I've got a problem. My 1990 xj with a 4.0L I6 and 180,000 miles (I don't know how accurate that is, because it has bigger tires on it and the speedometer is already off, so I bet my mileage is too) marks its territory, specifically, oil. Some guys I know told me it was a rear main seal going bad. Well, just as a quick temporary fix, I bought some rear main seal stop leak stuff for it. It seemed to kick in pretty fast (it said it should take 100 miles to start but it seemed to get right to work) and I wasn't noticing any leaks. Well, about 150 miles later (again, don't know how accurate cuz of my oversize tires) it leaks oil again. Crawled underneath it and sure garbage, its leaking oil between the transmission and the back of the motor, so that seems like a rear main seal, right? Well, my oil level is playing tricks on me. I went out one morning (with out starting the motor) and checked the oil and it was about 1/2 a quart low, well, I didn't add any cuz I didn't want to dilute the seal stuff. Well, the day I crawled underneath it, after it had cooled down, I checked the oil, and it wasn't even 1/4 of a quart low. And I pressure washed the whole thing like a month ago including the underside and it was almost brand new looking. Now it looks trashed with oil. So, I'm thinking about replacing the rear main seal next summer (because a guy I owns a shop that specializes in jeeps told me it's easier to take the whole motor and tranny out, and I need it for school), and this motor definitely in need of a rebuild, and it looks like it needs it sooner than I thought, and it also seems to be seeping oil out the front of the block . So I've got a 1991 xj with the same motor that the guy abandoned and we know own at the tow company I work at. The boss said he'll probably let me rip the motor out of it, he's not sure yet. This 1991 has more miles and all, so it probably also needs a rebuild. Tell me if I'm stupid for this, but my thoughts are is to take this newer motor, pull it, rebuild it during this winter and then next summer take mine out and drop the rebuilt one in mine; all this to basically reduce the time my jeep would be out of service replacing just a rear main seal and a few years after rebuilding the motor with the rest of the jeep. Eventually I think I might want to put a V8 in mine, but the I6 will do just fine for now. So my question is: how easy is it to swap out the motors from a 1991 with a manual transmission to a 1990 with an automatic transmission? Any other help would be great, like what might be causing it to seep out the front.

Thanks!

DFlintstone

Clean it good and watch close where it's leaking. The oil filter mound leaks right back there and looks like a rear main. Also you can change the rear main. Gasket and seal are about $30, but something has to be done about an oil pump gasket.