1974 cj5 t15a and dana 20 tcase - JeepForum.com
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post #1 of 4 Old 07-10-2011, 01:01 PM Thread Starter
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1992 YJ Wrangler 
Join Date: Apr 2009
Location: Washington st
Posts: 3
1974 cj5 t15a and dana 20 tcase

Hi guys I have been looking on the site and can not find the anwser to a problem a buddy is having. with his cj5 74 with a t15A and dana 20 tcase when he fills the tranny with gear oil it will over fill into the tcase why does this happen is the gasket between the 2 bad ? he serviced both filled to the fill plug drove about 10 miles rechecked tran was a little over a pint low.

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post #2 of 4 Old 07-10-2011, 01:22 PM
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1953 CJ3B 
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Location: Chesapeake
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Don't know about yours, but my T90/18 has a shaft seal
on the output of the tranny to prevent exchanging of fluids.
I would think all of them do to prevent mixing of what could be incompatible
hope that helps.....
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post #3 of 4 Old 07-10-2011, 05:35 PM
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2009 JK Wrangler 
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There should be a lip seal on the transmission mainshaft rear bearing carrier. At the rear end of the mainshaft is the input gear for the transfer case, which is held in place by a large nylock nut. The seal rides on the input gear. There should also be a paper gasket between the transmission and the transfer case that completely seals the two and prevents fluid swapping. I just had my CJ5's T150 and Dana 20 apart partly for this reason and found that the nut holding the t-case input gear was loose, allowing the gear to move and the seal to leak fluid into the t-case. Also, the last monkey that had worked on them had not only not torqued the nut properly, he'd installed the wrong gasket between the two boxes. The overhaul & seal kits sold for these boxes will include three gaskets. Use the one that has NO holes in it other than for the input gear and the mounting bolts.

This is a pretty simple repair that can be done with the trans still installed. The boxes both use the same 80w GL4 (low sulphur) manual trans oil, but the natural action of the trans will pump all the oil into the t-case, which will them puke it out from every seal, vent, etc. FWIW, there was a recall back in the day on this. The input gear seal was installed backwards on some transmissions.
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post #4 of 4 Old 07-10-2011, 06:34 PM Thread Starter
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1992 YJ Wrangler 
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Location: Washington st
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thanks we will look into it I was thinking there had to be something to stop the from flowing together
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