Tips on replacing a 4.0 rear main seal?


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I've been watching a bunch of youtube videos on how to replace the rear main seal on my 2005 TJ with an automatic. From what I gather, I can drop the oil pan and access the rear main seal that way. It doesn't look too difficult, although it is a bit involved.

-drain oil
-take off starter
-take off oil pan bolts and note where they go
-take off guide rail (long metal connector thing)
-remove top and bottom of rear main seal

I've purchased:
oil pan gasket (felpro)
rear main seal (felpro)
ultra black gasket stuff

My Jeep's oil leak has gotten progressively worse, and I don't think I can ignore it any longer.

Just looking for tips or feedback

Be sure you have the proper seal. Tab/no tab… keep track of rail bolts too.
I thought those that outline the pan gasket and punch holes to track the bolts used a good system.
Mark the bearing cap before removal to be sure it goes back the same way.
Pic and thin punch to help push out old gasket.

Use correct ft-Lbs to retighten everything.
You may need to loosen and drop exhaust so O2 wrench.

Never look down on anyone unless you are helping them up - Jesse Jackson
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Step one- start process
Step two-cry
Step three- punch transmission out of anger and cry harder

Lol but yeah listen to JPNinPA he knows what he’s doing

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I'm not 100% sure what you mean by the tab or no tab on the seal. Here's the seal that I bought. Does it look like the right stuff?


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Looks correct
Some sites parts lists are screwed up.

Drill down with year make model and came up with a part to an older 4.0 or 4.2

This will not fit

Same for my flywheel. They sent a 4 cyl flywheel not a 4.0 6cyl fly wheel

Never look down on anyone unless you are helping them up - Jesse Jackson
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What do you think about using both a gasket and some RTV? I've watched a few videos, and most just use a gasket, but this guy used a gasket and RTV at the ends

Idk. In the bottom only. Too difficult to get out of the top without pulling the engine. It may make it more difficult to remove again if needed.
The only place i used some is at the ends where upper and lower meet. And it was just a dab.

Never look down on anyone unless you are helping them up - Jesse Jackson

I think you're right. I watched one video and it was a guy cussing the person who did it before him (who put RTV everywhere).
Im 50% done. I managed to knick the top seal trying to put it in so I had to buy a second set.

I tried lubricating the top seal with dishwashing soap and water but it was still a real bear. Hopefully I can get it tomorrow.

I needed to wash my hair three times to get all the oil out.IMG_20220305_171422297.jpeg

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As long as you have the oil pan removed, do a check of the fore and aft movement of the crank. When I did my rear seal replacement (the first time) I found the crank movement to be twice the specified dimension. The thrust bearing (#3) was worn mostly on the rear side.
At that point I replaced all the Main Crank Bearings.
I've been told part of the reason the rear seal starts leaking is due to the crank moving fore and aft over time.

I have asked many folks in the know what causes the crank to have forward pressure on it, wearing the thrust bearing. I've not received a clear answer as to why it happens.

I finally finished this rear main seal job, and added it to my build thread:

I do have a question though. If you look at the rear main seal cap (think I got that terminology right) here:


You can see a light scoring, that you can feel with your fingernail. My engine has 165k miles on it.

I'm assuming this score is where the camshaft rides on that race, and has worn a mark on it - am I getting all my terms right? The whole thing is a bearing cap, and the metal insert is a race?

Finally, how bad are these wear marks for the life of the engine? My understanding is that you can't simply swap these out, as the are machined / mated to that part of the engine.
Rear main bearing cap on the crankshaft. This bearing should be smooth though some put grooves to increase lubrication. Yours is scored not terrible. See link below.
If you change one you have to change them all. The bearings are specific to the cap and bearing housing as well as the rod and cap housings.

Never look down on anyone unless you are helping them up - Jesse Jackson
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