79 CJ5 304 rear main seal repair - JeepForum.com
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Unread 01-06-2011, 04:49 PM   #1
kponytail
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79 CJ5 304 rear main seal repair

I thought I would start a thread on changing the rear main seal on a 304. Keep in mind I have never changed a rear main seal in a jeep or any other vehicle, I am a weekend warrior mechanic. I have read every thread that I could find on JF about rear main seals. I have used tips from all of them. I will take pictures and document each step. Jump in and let me know if there is a easer way or better way.

1) I chalked the wheels, unhooked the positive battery cable.
2) I unhooked the battery cable from the starter.
3) I removed both bolts from the starter and took it out and set it aside.
4) With the starter out of the way I loosened the passenger side motor mount, there are 3 bolts. One bolt has a ground wire attached from the block to the frame. I did not remove these bolts I only loosened them enough so when I jack up the motor it will only move about a 1/2 "





I will pick up where I left off Tomorrow evening.

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Unread 01-09-2011, 04:00 PM   #2
kponytail
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Today the first thing I did was drain all oil out of the pan

I jacked up the motor with a standard floor jack and a piece of 2x4


This picture shows how much seperation was needed from the motor mount to the block to get the oil pan off.


5) With the motor jacked up and all oil drained, I removed all the oil pan bolts.
6) with the oil pan bolts out I used a rubber mallet and a small pry bar to loosen the oil pan and had to finagle it around a little and it dropped down.
7) I now cleaned the pan up and gave it a fresh coat of paint.




I inspected the pickup tube and i looked good to me.


8) I now removed the main bearing and removed the old gasket from it




9) I am pushing the old seal out with a small wooden dowl I purchased at a arts and crafts store. I tapped on the dowl with a small wooden hammer.






With the seal removed I began to remove the old gasket


I must say the wooden dowl and hammer pushed the seal out with ease, everything went smooth today, but thats all I have time for today.
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Unread 01-09-2011, 07:50 PM   #3
brian613
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That's pretty much how its done. But there are some things I did different when I did mine.

1. I didn't remove the starter I just used a long extension to get to the oil pan bolts.
2. I didn't have to mess with the motor mounts on mine to get the pan off.
3. I wasn't lucky enough to do it in a garage I did it in my front yard.. so I envy you I had to do it all at once without stopping.LOL


One thing I would definitely inspect the oil pan closely where the bolt holes are. Its just like the valve covers if it gets tightened too much it will bend around the hole and will leak... if you have one or more that's bent you can take a couple of hammers and put one on one side of the hole and hit the pan on the other side and it will flatten the pan back out because it was smashed between the hammers. (You shouldn't hit it hard its better to use several lighter blows than one big one)
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Unread 01-29-2011, 04:40 PM   #4
Deadman 94 xj
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Good write up. I just placed an order from Morris4x4 for a seal and a lower gasket kit. I too have never done a rear main but it needs it.

The only thing I'm questioning is the quality of the morris4x4 seal. Not sure who they use but maybe Felpro is a better candidate.
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Unread 01-29-2011, 05:10 PM   #5
dzltech1
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how many miles on the motor,because that rear main bearing looks a little rough.Other than that you did good
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Unread 01-30-2011, 05:40 AM   #6
kponytail
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Quote:
Originally Posted by Deadman 94 xj View Post
Good write up. I just placed an order from Morris4x4 for a seal and a lower gasket kit. I too have never done a rear main but it needs it.

The only thing I'm questioning is the quality of the morris4x4 seal. Not sure who they use but maybe Felpro is a better candidate.
Deadman I used felpro, I just got everything back together and not a leak one (knock on wood).



Quote:
Originally Posted by dzltech1 View Post
how many miles on the motor,because that rear main bearing looks a little rough.Other than that you did good
dzltech the motor has 120,000 miles on it. I kinda thought the same thing, it looked rough but it runs quite well and does not smoke and the oil pan was quite clean inside. I just purchased a 1974 AMC 360 with a R4B Aluminum intake for $325 from a friend. I got it all tore down this weekend and it looks real good inside, it will be on its way to the machine shop Monday morning. This motor should wake things up a little.
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Unread 10-20-2011, 03:16 PM   #7
Greekcj5
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Seal Help

Hey guys and gals (if applicable),
I'm changing my rear main seal and I'm having a hard time finding the seals I need. What is the name of the piece that Kpony tail took off in the above pics that looked like a half moon bracket with a seal on it? I need the seal that goes on the outside of it. Thanks in advance
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Unread 10-20-2011, 04:27 PM   #8
davbytrace
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It is a main bearing cap, with main bearing installed.
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Unread 10-20-2011, 05:03 PM   #9
Greekcj5
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Sweet. Thank you
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Unread 10-21-2011, 11:28 PM   #10
1986cj
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If you need the seal that goes on the outside of the cap that should come with a pan gasket set.
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Unread 09-13-2012, 02:46 PM   #11
Armyguard91w
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When you fed back in the rear seal I take it you used the dowel rod and fed back in the new top part of the seal. Is there any other treatment that I would have to do to the seal when I change mine?
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Unread 09-13-2012, 03:15 PM   #12
ASteve
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I'll be doing this on my 304 in a month or so. I have the Fel pro gaskets as well http://www.summitracing.com/parts/FEL-OS30187C/ . Great write up, but where's the photos of the install?

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Unread 09-14-2012, 12:26 PM   #13
Greekcj5
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Ok guys and gals. Here's the latest update. I actually took the engine apart and my crank was pretty bad which is why it was leaking. I'm gonna get it turned, replace a few other bad parts i found and post pics when i can. Thanks for all the posts and support guys.
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Unread 10-28-2012, 03:11 PM   #14
Armyguard91w
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Okay question I removed the starter to replace drop the oil pan and found this. Well I don't think this hole is supposed to be there. If it is I can deal but if not how do I fix it?

forumrunner_20121028_161009.jpg
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Unread 03-29-2013, 05:58 AM   #15
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I just bought a 78 cj yesterday and have to replace the rear main seal, I too am a weekend warrior, Your pics are a great help, This is a great site with lots of generous help....
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