Is it really necessary to remove the transmission, converter & flywheel when replacing the rear main oil seal on a stock 258?

One book said yes, (the Jeep service manual) three others didn't mention it. However, the three that didn't mention it had the description of the rear oil seal in the "Engine Rebuild" section, meaning the engine would be removed anyway.

Any help or suggestions would be appreciated.:confused:

Your screwed!!! I was told that the rear main seal is (2) pieces and to get to the upper, the crank has to come down some. Mine was leaking about a quart every two days so I decided to just build a 4.7L stroker and chuck my old 258. Hope you can find better news, but this is what I was told.
Good Luck

Im in the same boat. My 258 has 10k on it and is leaking like a sive(sp) I put a rebuilt Jasper in it last march and it is leaking from the RMS already. I am quite pissed bc i really dont want to pull the engine again.

and like a dumbass i never filled out my warrenty papers for the engine. then again since i installed it myself i dont think they would have honored them.

God damn 258's ...

If it is a two piece oil seal you dont have to drop the the crank.First remove the oil pan then remove rear main cap.The lower seal half will remain in cap and the upper seal half will stay on top of crank.At this point use a blunt small dia. object to push the upper seal out and around the crank.The new upper seal will be pushed in and around the top of the crank.The lower seal half will replace the seal that is in the main cap.There will be instructions with the new seal kit.

The only thing I dropped to change mine on my 82 CJ was the oil pan. Its a pretty simple job. The hardest part was getting the oil pan around the engine mount. 2 bolts and the bearing cap comes off. Just put the one half of the seal in there. The upper half can betaken out using an awl or skinny screw driver to push one side of the upper seal around the crank. Once the other side starts coming out grab it with a pair of pliars and pull it out. Just be careful not to scratch the crank while usind the awl or screwdriver. I believe there is actually a kit that is made just to do this job, but you really don't need it. Put the new upper seal in the opposite way. Just keep feeding it around the crank till its in flush on both sides.

If its too tight to get the upper one in or out you could always loosen the bolts on the other bearing caps just a bit to relieve some of that tightness by dropping the crank just a bit.. Just make sure you have to torque them back to the proper specs.

Originally posted by Howdy
The upper half can betaken out using an awl or skinny screw driver to push one side of the upper seal around the crank. Once the other side starts coming out grab it with a pair of pliars and pull it out.



Use a small brass punch and it will come out no problem...your lookin at a 2hr job 6 :beer: maximum. :smokin:

Would a 90YJ have that 2 peice seal or is it a 1 peice?

2 piece!!! Replaced one in buddies about a year ago! Worked just as described above push out old roll in new!:beer: :beer: :beer: :beer:

I have done this the hard way.. Yes the brass drift attemp works some times. I however had to pull the motor (easier than the tranny) To shorten the story. I had the crank out and still couulnt get the bitch out, without pliers and yes it was a two piece seal. The upper piece was stuck to the block.:mad:

:) So far so good. The oil pan is off, the main seal is out, and nothing is damaged. This job has been straight forward so far. However... after stumbling upon the timing chain instructions in the service manual I've realized I need a new timing chain. The book says if it deflects more then 1/2 inch then it needs to be replaced. My deflects over 3/4", maybe even a whole inch. Anyway, sense I'll be buying a new timing chain I may just as well get a new oil pump while I'm down there.

I've got to be careful though. In about another day or two I'm going to be tempted to pull the pistons and replace the rings.

Anyway, wish me luck.

I'm failing misserably on trying to get the top half of the seal out of a 4.0 decided to take a beer break...... If I loosen all the mains will that release enough pressure off it or will I need to seperate the transmittion (5spd)?

I have no suggestions. Mine came out with only a little tapping with a punch.

I will say that putting the new one in was a little harder. I was also surprised to see that the edges of the block peeled off some of the seal as I pushed it in. I guess it's a custom cutting feature of the 258 block. Now, I wish I could say that all is well, and it aint dripping a drop. But I can't. As it turns out this project has snow balled and exploded in my face all at once. :nuke: Not only does the oil pan seal leak at the timing chain cover, :mad: but the fuel pump has gone bad. :eek: How do I know the fuel pump is bad? Well, when the fuel pump squirts fuel all over the oil filter and motor mount, it's bad. I also had to spray carb cleaner into the carb just to get it to started in the first place. It idles nice though, the new timing chain was a good idea.

Just a tip for those considering a timing chain replacement or any front oil seal work. Put the timing chain cover on before you put the oil pan on. The timing cover needs room to center itself at the front oil seal, this is difficult to do with the oil pan in the way.

P.S. It's tough to work on a Jeep when you've got two small kids. And yes, this project has taken almost a month. (for those checking dates) I need a f...k'n :beer:

It it is giving you real trouble have a helper rotate the crank as you tap the seal. also they make a little tool that screws inito one end and pulls it out. I don't like 'em 'cause if you break the seal you are SOL. It can be a pain but I have never had one I could not get out with the crank in and about the back 2 mains loose....yet....

2 hr Beer break over- I'm already over Thumpers timetable. I'll try loostening all the mains and try again. No help avail to rotate tonight and I'm too stubborn to wait till tomarrow- but thanks for the suggestion. If it's this rough to get the stinkin thing out, how the He!! I'm ever going to get the new one in in without destroying it is beyond me.