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> Jeep Articles > Technical & Installation - Engine / Drivetrain > 4.0 Rear Main Seal Replacement

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Technical / Installation Articles - Engine / Drivetrain

4.0 Rear Main Seal Replacement

Article written by Moab Man

Date Added: 05/30/2006

Replacing the rear main seal in your 4.0 inline 6.

Anyone who has a high milage 4.0 knows how prone the rear main seal is to leaking. Don't worry, though, it's not that hard to change. We'll walk you through it.


1. Remove oil pan

2. Remove furthest back bearing cap

3. The seal is in two halves: bearing cap and engine block

4. Using something plastic, so you do not scratch anything push the top part out. It will be a semi rigid half circle.

5. Using something plastic, so you do not scratch anything push the top part out. It will be a semi rigid half circle.

6. Carefully note how it goes in there. I have heard, and just recently confirmed, you can actually put it in backwards.

7. Put the new one in, lubricating it with some liquid hand soap. DO NOT use one with grit in it!

8. Remove bottom half from bearing cap and press new one in.

9. Remove bottom half from bearing cap and press new one in.

10. Reassemble bearing cap torque to 80lbs. CRITICAL TO USE A TORQUE WRENCH

11. Use a small amount of RTV gasket seal to tack the oil pan gasket in place.

12. Reinstall oil pan. Pan will have two different size bolts 1/4X 20 torques to 84 INCH lbs and 5/16X 18 torques to 132 INCH lbs. Since I don't own an INCH pound torque wrench I tightened them to being snug but not crushing the rubber oil pan gasket.

13. One more thing, use the smallest amount of RTV sealant on the ends of the bottom half that will touch the two ends of the top half. DO NOT use enough that it will ooze anywhere.

14. Additional stuff...

Buy your rear main seal from the dealership. I can't tell you why it is but I have had the best luck with them sealing when they have come from the dealership. They are probably made by the same company but I don't screw with good mojo when it works.

15. Make sure when tightening the bearing cap you do the right one. I have witnessed people time and again tighten the bearing cap forward of the last one where the seal is.

16. When you open the bearing cap there will be a bearing shim. DO NOT scratch it/drop or turn it around. Must go back the way it is because of how it has worn.

17. Don't be surprised if it doesn't seal the first time. It's kind of a hit or miss thing. Just a poor design IMO.

18. It will leak a little for a couple of days until the oil causes it to swell a little bit and everything becomes seated in there.

19. Remove any liquid had soap that gets on the end points where the top and bottom halves will touch. This will stop the RTV from sealing well.

20. You will need a new oil pan gasket.

Final Thoughts

If you have any questions feel free to ask. I am the master of the 4.0 rear seal.

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