As the title implies, I have replaced my front main seal... 6 times in around 2 years. The problem originated after my original harmonic balancer disintegrated and was replaced with an Omix Ada pulley.

My seal tears and leaks within the first week after replacement, everytime. I've become extremely proficient at the fix, I can swap my seal out in about 20 Mins at this point but it can't be good for my crankshaft among other concerns.
Here's what I have:

• Remanufactured 4.0 from Marshall's Machines in Maine with ~40k miles on it.
• Rebuilt Ax15 from Canton transmission in GA w/ ~40k mi
• NP242
• Stock drivetrain, etc.

Here's what I've done about it:

• I've asked every jeep 4.0 enthusiasts and expert I've run into for 2 years about this problem so if you can solve it then you'll be the premiere jeep 4.0 extraordinaire - in my book, anyways.
• I've read any relevant forum thread across every jeep site I can fin
• watched all the available videos on the proces
• replaced the timing cover, thinking was "maybe the Journaling of the cover is off and causing a pinch"
• replaced the harmonic balancer with 2 different brand
• replaced my transmission mount, thinking vibrations from the trans were carrying thru the crankshaft
• Checked the thrust bearings, checked the shaft for damage or wear while I was at it, none seen. However I'm not a mechanic so I don't know what exactly I'm looking for besides painfully obviously scars.
• ensured each new seal goes on with ample lubricant followed by a well lubed HB, every replacement
• called Marshall's Machines in Maine and got a "we ain't ever heard of that issue. In 300 engines I've never had that problem sorry bud.
• I am positive the seal is going in the correct way, every seal I remove has obvious tearing or damage not caused by the removal process. I can post pics of my most recently removed seal later.
• The HB bolt is absolutely torqued to spec everytime

One thing I've yet to do but will do one of these paychecks is motor mounts. currently the mounts are surprisingly decent, but I've long since past the point of reason and warmed up to the idea of firing the parts cannon at my cherokee in very liberal volleys. Any of you reading this can suggest almost anything and I'll try it.
This seal has become my Moby Dick and I will sink this damn ship to kill this leak

 

All i can think of right is the wrong seal is being used for your application. Where are you getting them and what part numbers?

 

I've bought a National brand seal everytime I can remember. Occasionally from advance auto, other times from rock auto, and once it was included in a Felpro timing cover kit. I don't know if anyone else makes this seal, but I will definitely try another.
I can provide a part number in an hour or 2, but until I'm home, here is what I hope is a helpful link - https://www.rockauto.com/en/moreinfo...999&cc=1180268

While copying this link I did notice that BCA makes a seal as well, that I will probably try next.

 

OEM

 

1) are you absolutely certain the seal has not worn a track in the crankshaft

2) I would apply a dial gauge to the shaft outer, to see if there is any runout, which will cause a seal to fail

I would inspect the surface with x20 Loupe, under very bright light...if you can get close enough to look

its interesting to look at a metal surface at that mag, you will see if it is damaged..ie whether a bearing has turned within or upon its mating surface

 

I'm as sure as I currently can be about what you asked, but some of the concepts you suggested are new to me, so I'll start looking into those so I can try them out.
My overarching concern is that when I HB seperated originally, kicking off this issue, the forces warped my crankshaft. If not that, an otherwise harmless auto accident I was in a few month prior. No way to be sure they aren't connected.

 

Exactly. Before trying another replacement, I would pull the damper and check for both runout and thrust with a dial indicator. How many crank dampers have you installed on this crank? and are you sure you are aligning the cover/seal properly so the damper doesn't smash the seal?

 

The keyway for the crank has to be siliconed into place and you are supposed to put some silicon on the crank pulley keyway slot to keep it from leaking through the keyway. In addition, since you say the seal is damaged. I rebuilt my 01 last fall and purchased a "new " timing cover from Advance? maybe. ALL the bolt holes were OVERSIZED by a good bit. I had to press in bushings and redrill them to make a really nice concentric fit. I hate to say it but pull the bolts out one at a time and screw in a long test bolt to see if it is centered in all the holes odds are that you are resting on the edges on some and the crank is no longer centered in the seal