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  #1  
Old 07-25-2008, 06:44 PM
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FSJeep13 FSJeep13 is offline
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How to replace rear main seal?

Hey, I'm pretty sure my rear main is bad. I leak oil like there is no tomorrow at times especially now that the summer heat is beating on us. I brought the jeep in to get the oil changed and as I watched the oil puddle accumulate I wondered why I was even there...

I read the tech article here, but my question is, Do I have to take out the engine to replace the seal? or maybe transmission and Tcase? The "friends" I have at the jeep dealership told me it would be more worthwile to not fix the leak and just buy a new engine for what it will cost me. Sounds like a load of carp to me. So, can I just get under there and replace the thing? Thanks guys. Any pics would help too.
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  #2  
Old 07-25-2008, 06:56 PM
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You do not need to pull the engine or buy a reman to fix the leak. Just follow the instructions and you can change the seal with the engine in the Jeep.
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  #3  
Old 07-25-2008, 07:00 PM
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AlsChopShop AlsChopShop is offline
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they are blowing air up your skirt.

pull the oil pan, remove the rear main bearing cap, pull the old seal out, push the new one in, reinstall bearing cap, reinstall oil pan.

Al
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  #4  
Old 07-25-2008, 07:21 PM
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dmnit! I knew I shouldn't have worn that in there.
I checked at the back of the valve covers to see if there were leaks there. I forgot to check at the heads. I found a red oily fluid on the back of the intake. Must be ATF. I know the filler is back there... I do leak enough of ATF as well. hopefully that is just another gasket or seal.

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2000 TJ I6, Borla header, 3.5" lift, 33x12.50 BFG ATs

1978 Wagoneer, 401. 2"BL, 7" SOA, chrome steel wheels/ 33x12.50 BFG ATs, and tachometer hopefully done soon.
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  #5  
Old 07-25-2008, 07:33 PM
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bushwood44 bushwood44 is offline
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hopefully its the trans pan gasket instead of trans pump seal(probably both)
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  #6  
Old 07-25-2008, 08:03 PM
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The rear seal change is a cake walk, if your half way mechanically friendly. On mine I just jacked the jeep up by the frame (lets the axle droop away from the engine for more room). Pulled the pan and rear main, changed seal retorqed and reassemble. The most challenging part of the whole thing is putting the pan and pan gasket back up. That's always easier when the engines out, unless you're in a gravity free zone . Good luck you'll do fine.
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  #7  
Old 07-25-2008, 08:33 PM
intenseimages intenseimages is offline
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these guys are halfway right on how easy it isnt. lol

here is the way it usually happens:

go to store buy parts,
stop at next store pick up drinks of choice
go home, drain oil
drop pan
drop rear main bearing cap

next step is to spend 3 days dropping crap on your face while trying to get the frozen in place rear main seasl out of engine.

once it is finally out though it is a matter of rolling new seal in and bolting it all back up (please remember te re-install drain plug) and filling wiht oil

eric
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  #8  
Old 07-25-2008, 09:01 PM
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sweet. I'm excited. I thought this was going to be a real downer! People were telling me, "yeah you better just rebuild the whole engine while you have it out to do the rear main..." blah blah blah. thanks guys
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2000 TJ I6, Borla header, 3.5" lift, 33x12.50 BFG ATs

1978 Wagoneer, 401. 2"BL, 7" SOA, chrome steel wheels/ 33x12.50 BFG ATs, and tachometer hopefully done soon.
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  #9  
Old 07-25-2008, 09:24 PM
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srobertsfsj srobertsfsj is offline
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Shimniok and I did the one on my J20 a couple years back and it wasnt that hard. A couple of tips he gave me were to remove the rear bearing cap and loosen the next bearing cap. I also bought some soft brass rod and used it to drive out the old seal. The soft brass shouldn't score the block. And make sure you tighten the bearing caps down to the correct torque.
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  #10  
Old 07-26-2008, 05:46 AM
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caionneach caionneach is offline
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to make it easier...

Can't believe the guys aren't telling you this:

To make it easier to get the top half of the seal out, you need to drop the crank, otherwise it can be a PITA.

To do that not only do you need to follow the manual and loose the bolts on all the main journals, but you also need to LOOSEN THE BELTS ON THE FRONT OF THE ENGINE.

The belts maintain upward pressure on the crankshaft, and loosening the belts makes it all easy.
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  #11  
Old 07-26-2008, 06:51 AM
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JERSEY JOE JERSEY JOE is offline
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REAR MAIN SEAL REPLACEMENT

Also you can back off the main cap screws to drop the crank a few thousands. Also the most important thing is to make sure the rear main cap is clean and put silicone sealer in the chamfer between the cap and the block. If you do not do tis you will be doing the job twice.

READ THE INSTRUCTIONS IN THE JEEP SERVICE MANUAL AND FOLLOW THEM TO A TEE. SOMEONE HERE CAN POST THE PAGE FOR YOU.

It is easier with the motor out or if you leaving it in beg borrow whatever, get access to a lift. Doing this job on your back is more of an adventure than you want especially for a novice.
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  #12  
Old 07-26-2008, 08:04 AM
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I did the rear main seal...took 5 hours and it still leaks. My mechanic would have done it for $185...would have been worth it. But, I learned a lot -- like I have no business under a Jeep!!

Hey, if your Jeep place can replace an engine for $185, go for it
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  #13  
Old 07-26-2008, 08:16 AM
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caionneach caionneach is offline
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Ditto what Jersey Joe said

Following the instructions assiduously (also known as "to a tee") is very important.

--the rear main journal area must be clean (use brake cleaner as needed, so have several cans ready)
--if the rear main area isn't clean the RTV on the areas as specified (joints of the upper and bottom seal, chamferred areas on the rear main cap) will not make a good seal.

But other than that it's easy. If it looks clean, assume it's not and use brake cleaner to make sure.
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258 cid/T-5 $15 Sunpro Voltmeter gauge
replacement; Quadratec Trailmax Thermal Pro
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  #14  
Old 07-27-2008, 08:38 PM
Sbonley Sbonley is offline
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Also make sure it is not the oil galley seal at the back of the block. Those are notorious for leaking and it looks like a rear main seal leak because of its location.
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  #15  
Old 07-27-2008, 11:26 PM
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4x4fEvEr 4x4fEvEr is offline
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what? you guys are making it sound hard! its not. your mechanic friends saying rebuild or get a new engine must think it has a one piece rear main seal and in that case you would need to pull the tranny or pull the engine, but AMC's are two piece seals so like most have said just drop the pan take off the main cap and loosen the next one. pull off the bottom part of main seal and then use a punch or something similar to start the top half of seal . then do the reverse for putting it back on. make sure u get the lip on the seal facing the correct direction and be sure to torque all bolts back to specs. the biggest pain is getting the pan back on for sure.
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  #16  
Old 07-28-2008, 08:14 AM
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My only suggestion it to let the oil drain overnight or longer. Nothing worse than oil dripping on your face.
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  #17  
Old 07-28-2008, 09:13 AM
FSJ Guy FSJ Guy is offline
 
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Also, depending on our Y pipe configuration, plan on dropping the Y pipe in order to remove the oil pan AND access the rear seal. If they haven't been off recently, the manifold studs and nuts will be frozen together. PB blaster those suckers for a good week before you start. Otherwise, you'll be removing your manifolds to take them into the machine shop to have broken studs removed. AMHIK.

Watch your seal orientation and lube the seal with fresh oil when you install it SLOWLY.

Have fun!
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  #18  
Old 07-28-2008, 09:46 AM
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And bring LOTS of rags/cleaning supplies to the show! You'll spend more time cleaning before you put it back together than you did fixing it!
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  #19  
Old 07-28-2008, 10:10 AM
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"READ THE INSTRUCTIONS IN THE JEEP SERVICE MANUAL AND FOLLOW THEM TO A TEE. SOMEONE HERE CAN POST THE PAGE FOR YOU."

Soooooooooooo, can someone please post the Service Manual Instructions. That way we can all be in the know!
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  #20  
Old 07-28-2008, 12:54 PM
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Quote:
Originally Posted by 4x4fEvEr
what? you guys are making it sound hard! its not. your mechanic friends saying rebuild or get a new engine must think it has a one piece rear main seal and in that case you would need to pull the tranny or pull the engine, but AMC's are two piece seals so like most have said just drop the pan take off the main cap and loosen the next one. pull off the bottom part of main seal and then use a punch or something similar to start the top half of seal . then do the reverse for putting it back on. make sure u get the lip on the seal facing the correct direction and be sure to torque all bolts back to specs. the biggest pain is getting the pan back on for sure.
Yeah...what he said. The pan removal and installation is the hard part.

DO NOT use a steel drift to drive out the upper part of the seal. Even if that's all you have on hand. Plastic or brass ONLY. If you knick the crank it will leak at the RMS forever.
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