First I gotta say I put the title like that because it was the first words that came to mind. But thew main thing is with the tail housing extension removed there is mass amounts of fluid come out of my trans. It looks like there is a hole at the 6 o'clock of the back side of my trans and fluid just keeps coming out. I rebuilt it for the first time and read I needed to put 12 quarts of fluid in and I did. Then I saw tons of fluid coming out that I couldn't explain. Is the hole supposed to do that like for an overfill thing> and if not where does that hole go and can I just fill it with something?

 

Might need to replace gasket, had one fail on me and ruin my transmission

 

There is a lube "squirter" orifice hole in the back of the case on all 4L60E family of transmissions. It is designed to squirt lube oil to the rear extension housing bushing.

If you have a leak coming from in-between the case & the extension housing. it's probably a missing/bad square cut o-ring for the extension housing.

If it leaks at the slip yoke. You either have a bad extension housing bushing/seal/slip-yoke.

If this is an initial fill and you put more than 5 qts of fluid in it while it's not running. You have it coming from the vent tube. Some have a piece of hose long enough for it to appear to be right at the rear of the case but it's not really.

Initial install/fill should go like this:
Step 1) Pour 1 Qt into the converter and install to the unit.
Step 2) Install the transmission assembly.
Step 3) Pour 5 qts into the pan, get 5 more ready to pour. (you want this on the level with the wheels off the ground for the rest.)
Step 4) start engine and pour the other 5qts in
Step 5) check fluid level, its probably not on the stick yet.
Step 6) Pour an additional 1-2 qts of fluid in and run through the gears (R, N, D, 3, 2, 1) it should shift through all gears at this time.
Step 7) check fluid level and make sure it is at the bottom of the cross-hatch area of the stick. Time spent running through the gears give you enough time for residual fluid to run down the bent part of dip stick and not alter your level check.
Step 8) Lower vehicle and take for a road test. Recheck fluid level after road test, it should be at the top of the cross-hatch area at this time.

Hope this helps.

 

 

In the last picture you can see the "squirter" orifice at the 7 o'clock position. The one in the very bottom is a drain back hole. It is used to let the accumulated fluid in the extension housing to drain back to the pan. It will drain like that if it has enough fluid to do that. Both of those are required and are sealed from leaks by the extension housing o-ring and rear seal. They are normal.

I'm trying to understand the real issue.

In your original post you stated

"I rebuilt it for the first time and read I needed to put 12 quarts of fluid in and I did. Then I saw tons of fluid coming out that I couldn't explain."
If you put 12 qts of fluid in it without it running and the extension housing on a 2wd or the TFC adapter/TFC on a 4x4 are not bolted up the the back of the case. your gonna have massive leak because there is no way to contain the fluid.

Do not fill the drain back hole with anything. Doing that would cause the extension housing or TFC adapter to fill up with fluid and have no way to go back to the pan to be circulated... Eventually it would blow out the rear seal or extension housing o-ring and possibly burn up the transmission from low fluid in the pan.

Put the extension housing on it and seal up that area. Then you won't have a leak from that hole.

 

So the main issue I was having was that the extension had 2 quarts of ATF in it and was leaking to the back towards and down the T case and all over the floor. I had no idea why it was doing that. I would assume it was the amount of fluid I put in. I only ran the engine for about 5 seconds but tried staring the engine a few dozen times. Just a little more info I rebuilt an LS engine as well as the trans but like I said ATF started leaking out but I didn't know why. If it's just the amount of fluid then that is manageable. But I thought the Extension was supposed to be a dry cavity?

 

Now that I know it's a 4x4 I can reference things correctly.
The rear of the transmission is sealed by the transfer case adapter and the TFC (transfer case) by 3 seal points. The TFC adapter has a (1) square cut o-ring seal against the transmission case and (2) a gasket against the TFC side of the adapter. The TFC has a (3)double lip seal for the TFC input shaft. That seal keeps transmission fluid from getting into the TFC and the special TFC fluid from getting mixed with the transmission fluid. The area inside the TFC adapter is supposed to be lubed or wet. If you are missing 1 of those 3 seal points, you will have a leak.
I have in the past known Dodge guy's to leave the TFC adapter gasket off on a GM. Dodge uses a seal at the back of the transmission and the TFC. There is no gasket there on a Dodge but GM does.
That is why I explained in detail, the fill procedure. If you put more than about 6 qts of fluid into a dry transmission & converter, it will leak from the vent. If you don't have the TFC attached to the back of the transmission it will come out of the rear drain back hole sooner.
The service fill of a deep pan 4L60E is approximately 5.5 qts. Total fill is about 13. If the cooler lines and transmission cooler are flushed, you can add an additional 1/2-1qt. of fluid.

 

I replied to OPs other thread where he gives very little information about what was leaking. Tranzman is dead on with his info.