Oil pouring out of transfer case fill plug...

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Nov 26, 2013
An alarming title but…this is with the plug out! So, I had hooked up a bypass tube between my tranny and transfer the other day and had both fill plugs out to do it. A slight trickle was coming out of the transfer. It didn't seem to stop after 5 minutes (tiny thread of a trickle) but I assumed it was just dripping down from the gears or something and that there was pretty much the correct amount of oil in there. And dipping my finger in the tranny fill hole I could touch the oil. So all seemed good. I installed my bypass hose…and since then, I noticed a small leak from the connection of my hose onto the transfer case. So I took the banjo bolt out of the transfer plug hole to tighten the hose connection and suddenly a lot of oil started flowing out and hadn't stopped even after a minute or two (probably lost about half a cup). I put the plug back in to stem the flow and came on here to saywhat the heck is going on? How is it the oil levels were fine when I had the two plugs out previously…and now suddenly oil is appearing from…somewhere? I have not yet checked the transmission oil level as I wanted to ask advice here first. Any takers?
I feel your pain. I had the same problem with the 78 model last weekend. I pulled the transfer case plug slowly with a catch pan and it drained out a quart and a half. This probably came from the transmission. I checked the transmission first and it was low. I didn't put more in the tranny because I was going to do the bypass hose but now you are having the same problem with the bypass line. I don't think I will be going that way now. I guess I will fix it the right way and do the seals. From what I have read on here the T case usually pumps oil into the tranny when the seals are bad not the other way around. Logic tells me the oil will drain from the higher point to the lower when not under pressure. That is what is going on when it sets still. So you might want to check the tranny level before adventuring out again. Good luck.
Yes, I have had the oil pour from the tranny in previous instances. It seems the bypass hose has changed something. If I have both the plugs out, obviously there is no pressure and I don't get oil pouring out of the transfer but once the truck is running, well, of course the oil heats up and I suppose some pressure arises. I'm not really in the mood to be changing seals, I can surely say that….Tomorrow I will check the tranny level and surely it will be low. Hmmmmmm
There should not be an appreciable amt of pressure in there. The T-case vent should eliminate any pressure build-up. A very strange situation here. I have the bypass hose installed as well, but have not done the Tx/T-Case oil check yet-both were full when the hose was installed, and there is no evidence of external leaks(sounds like I need to check this asap)
Well people have been running these bypass hoses forever with no problems, so it seems. It occurred to me though…if there is no pressure in there…and if the oil from the tranny ends up in the Tcase…it will just stay there, won't it? There is no pressure to push it up the hose so your tranny is going to be starved. Or quite possible I am not understanding the principle of how the hose does its job.

To be fair, I have leaks from both the back of the Tcase and the front of the tranny and I guess between the two on the inside, also, since the oil is migrating. Sounds like Swiss cheese. It was a leak from the newly installed bypass hose, however, that got me under there today.

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