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Topic Review (Newest First)
05-15-2013 12:56 PM
rear main replacement

Yes can leave in trans--just remove the tube crossing underneath makes easier going back in. Trick to removing old seal is loosen cap nuts on crankshaft first couple of cylinders (from seal) and while removing and re installing, have a helper turn over the crank with a wrench/breaker bar(removing plugs helps with this as well) and note the position the lip on the old seal as it comes out to make sure you put the new one in in same orientation. Use once pc rubber pan gasket and ensure proper seating of same at transmission end. Biggest headache is cleaning of surface of pan on the block for the new gasket!!!
05-15-2013 11:02 AM
Originally Posted by Cashcrazy View Post
You're welcome. The valve cover is easy. There is plenty of info on the RMS but I didnt find one with the trans out. I get a little nervous about hitting the crank and causing a burr. I hoped I could get the top portion out easier.
I'm planning on using a bamboo skewer to push the top seal out. Bamboo is very hard, but not hard enough to scratch the crank. Like you only concern is scratching the crank. There also was a good idea for inserting the new top seal using a soda straw cut at an angle to get the seal started. You slide the edge of the soda straw into the groove and feed the seal through it, this keeps from tearing the new seal on the edge.
05-14-2013 10:08 PM
Cashcrazy You're welcome. The valve cover is easy. There is plenty of info on the RMS but I didnt find one with the trans out. I get a little nervous about hitting the crank and causing a burr. I hoped I could get the top portion out easier.
05-14-2013 10:03 PM
SmugglersBlues I'm glad you asked this. I'm scheduled to send mine in to have the RMS done. They quoted me between $500 and $750 to do it. I think I'll try the valve cover first and see if that works. Thanks for posting.
05-14-2013 09:53 PM
Cashcrazy Thanks for the responses. The valve cover gasket is new and not leaking.The RMS is not a big issue right now, but if it is easier to replace while i already had the trans pulled then i would go ahead. I have several small leaks on the front I'd like to tackle first. Bottom radiator hose, one of the power steering hoses, and the oil dip stick is leaking where it goes in the block. This jeep is a one owner jeep that I bought about a week ago. Twenty four years of sitting in a garage with little driving has caused a few leaks from dried out rubber. The jeep addiction continues...
05-14-2013 09:26 PM
tigerblood I havent changed mine yet, but will soon, Ive done my homework on the subject and removing the trans is unneccesary, check out the video on youtube of the guy doing it on a cherokee 4.0
05-14-2013 09:07 PM
mike_b_ar I replaced mine. It's really pretty easy. Having the transmission there was not a problem at all.

One thing to consider before doing it though, the 4.2 is notorious for valve cover leaks, especially at the back. These look like a RMS leak because of where the oil comes out. I replaced the RMS and leak continued. I replaced the RMS again, thinking I had done something wrong, and the leak continued. I replaced the valve cover, no more leak.
05-14-2013 01:52 PM
1989 YJ 258 Rear Main Seal

I am considering replacing the rear main in my 4.2. It's not leaking bad, but it is not going to get better with age. I found lots of info for changing this on google with the transmission still in the Jeep. I will be replacing the output seal on my tf999 and the tcase input seal in the next couple of weekends. Will removing the transmission make replacing the upper portion rear main a lot easier or is it really about the same with more working room? I'd appreciate any advice from someone with hands on experience. I don't want to bother pulling the trans if there isnt much benefit.

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