Replaced a steady oil out of the AX5 tail -

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post #1 of 3 Old 11-09-2013, 05:15 PM Thread Starter
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1995 YJ Wrangler 
Join Date: Feb 2013
Location: Austin
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Replaced a steady oil out of the AX5 tail

Short version...I have a pretty massive oil leak out of the tail of my AX5. I replaced the seal, and I'm out of ideas.

Long version...
In the midst of several upgrades (Tummy Tuck, Ford 8.8 swap), I changed my NP231 from the factory original to one I purchased from a local Jeep friend, since it already had an SYE installed. Both my original NP231 and the SYE 231 replacement had 21 splines. They appeared to have the same input gear length, but I didn't measure them. Basically, they appeared to be identical.

I initially installed the SYE 231 with a clock ring. After a short test drive on Wed night, I had a steady stream of oil out of the tail of the AX5. I believed that the extra thickness of the clock ring caused it not to seal, or that I had a bad seal.

Today, I tore everything out, and drilled holes in the AX5 flange, so that I could remove the clock ring. I also replaced the AX5 rear shaft seal. I reassembled everything, and went for another test drive. It still leaks oil. It's not a's a pretty steady stream.

There's no doubt that I'm going to pull the NP231 back out again, but I'm not sure what to do differently to solve the issue. I bought a new seal, so I'll replace that again. I could understand a bad seal causing a little drip drip drip, but I'm seeing a steady stream.

I should also note that I never had an oil leak with my original NP231 installed. Also, the SYE 231 works fine - no issues and no leaks. It's leaking 10W30 out of the AX5, not ATF out of the NP231. I attached a picture of my original NP231 input gear.

Any thoughts/ideas/suggestions? Thanks!

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post #2 of 3 Old 11-10-2013, 09:24 AM Thread Starter
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Location: Austin
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I pulled the SYE 231 back out of the Jeep, and didn't see any obvious problem that would cause the AX5 leak.

The two transfer cases appear to be identical - the input gear diameters are the same. The extension is the same.

The original 231 is on the left - the SYE 231 is on the right:


SYE 231:

At this point, I'm planning to carefully polish the input gear sealing surface, and replace the seal again. Should I use RTV on the outside surface of the seal when I replace it?

Any other ideas or thoughts? Thanks!
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post #3 of 3 Old 11-10-2013, 10:03 AM Thread Starter
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Here's a couple of pictures of the AX5:

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