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Unread 03-12-2012, 08:53 PM   #1
Blacky15
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1985 CJ7 
 
Join Date: Mar 2010
Location: Moorhead, Minnesota
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Dana 20 T-Case leak

I have a AMC 360 bolted to a TH400 and then a Dana 20 Tcase. My tranny was rebuilt a year ago and I rebuilt the Tcase myself. I am having my Tcase fill full of tranny fluid and then my tranny will stop engaging until I put more fluid in. Question is does the Dana 20 from a IH Scout require gear lube or does it use tranny fluid? And then how hard it is to replace the seals in the tranny and Tcase to stop this pain in my ars?

Thanks for the help!

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Unread 03-12-2012, 11:47 PM   #2
mmerlinn
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Huh? The transmission fluid is separate from the transfer case fluid so HOW does filling the transfer case have any effect on how the transmission shifts?
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Unread 03-13-2012, 12:17 AM   #3
jnicewan
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Quote:
Originally Posted by mmerlinn View Post
Huh? The transmission fluid is separate from the transfer case fluid so HOW does filling the transfer case have any effect on how the transmission shifts?
I think he is saying the TH400 is leaking ATF into the Dana 20.

Anyway the dana 20 takes gear oil. I am not too familiar with the TH400/D20 combo so I am not sure which one and maybe both have had a seal failure. A lot of the time the only seal is on the T-case input shaft, but some trannys have an output seal too. Whichever it is, you can replace the seals after you seperate the case from the trans.
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Unread 03-15-2012, 05:12 PM   #4
Blacky15
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Thank you jnicewan you are correct. I have having my tranny fluid flow into my dana 20 transfer case and then out the output shaft of the transfercase. Does anyone know if the TH400 has a rear seal or if it is just the Dana 20 input shaft seal that needs to be replaced??
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Unread 03-27-2012, 11:10 PM   #5
mmerlinn
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No rear seal on a 400 transmission.
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Unread 03-28-2012, 09:47 AM   #6
Blacky15
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I pulled the two units apart and there is no rear seal on the th400. mmerlinn is correct. What I did find was that there was no O-Ring on the tailshalf of the th400. It the shaft that slides into the Texas style adaptor bracket. Not sure if the o-ring tore or what but i couldnt find it anywhere.
After installing the new o-ring I beleive I now have a non-laeking th400/dana 20 combo.

Thanks everyone for the help. Gotta love this site!!
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Unread 04-04-2012, 09:57 PM   #7
RockHands
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Was it a "big" leak? I am trying to run down a small leak at the interface of my th400 and Stak 3-speed. Just curious before I try to pull it all apart.
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Unread 04-05-2012, 12:32 AM   #8
Blacky15
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It's wasn't big like all over the place it would only leak when i was driving and there pressure would push the fluid into the transfercase and out the overkill vents. But since the oring went on I'm drip free. Real easy fix too
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Unread 04-05-2012, 08:59 PM   #9
RockHands
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Drop the T-case and there it was?
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Unread 04-06-2012, 11:10 AM   #10
Blacky15
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The missing O-ring on the tailshaft of the th400. There is a groove ground down spot for it midshalf. If you're looking for it you cant miss it.
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