Easy test to see if it is tranny or tcase. If the light comes on, unplug the 2 prong sensor on the tcase. It's easy access.
The tranny sensor is up on the cooler in front of the radiator. It's a little harder to get to....also I should mention that the sensor can go bad too

 

i toight it is the transmission fluid first but when i unscrew the filling nut, it started to pour out so it was full...
not i am trying to locate the transfer case to refill it.
yes, 15 was the one which ligthted up in the begining if the trip. but after putting it into N and leave if for few minutes, light turned off.

 

The transfer case and transmission are both link to that light. The best way to eliminate one is to unplug the easy access sensor on the transfer case the next on the light comes on and see if it goes out

 

awesome! thank you very much! i located the plugs, so i am gonna add some fluid now and see if it helps.
there is just one of these things that i need to fill right?

 

Yes one fill hole for tcase. Put in oil until it starts coming back out
Tranny has one but fill procedure is different.engine running/ fill/ go through gears/ fill

 

i filled the t case without an issue, i was cursing at the designer which located the brake cable right infront of the lug til the end of the task i had just 3quarts and it still didnt fill up all the way but this should be enough to take me back to san antonio (about 150 miles).
thank you everyone for all the help. i cant explain how much i appreciated.

 

I strongly urge you to drain all of the fluid from the transfer case and fill the proper amount.

When you ran the t case low you caused metal on metal wear which had created metal shavings in your t case. If you drive it with the metal in it and low you will cause more damage than you already have.

Repeat, I STRONGLY urge you to drain and refill before driving 150 miles.

 

so I finally flushed the tcase yesterday. there was some metal scrape on the bottom plug but not to the extreme, it filled it with fresh gear oil(it took about 4 quarts, it was already spilling out after the 4th quarts). when I was searching for stop leak kind of product for tcase, I came up to this and people wrote so many reviews stating they used it in tcase without a problem is that correct, is it safe?

 

yes, I works by swelling the gaskets and seal, just be sure you get the right product as they sell a half dozen products for different types of leaks

 

The picture you provided is the transmission pan and uses transmission fluid as you have pictured beside it. The transfer case uses gear oil, thicker than regular motor oil, harder to get to the fill plug of the transfer case that is up higher near the floor of the vehicle with the e-brake cable in the way to get to the fill plug. Take e-brake off to make the cable more flexible to get a wrench in to the drain plug.

In regard to the transmission being full, you need to check this with the vehicle running. Fun I know, but if you open the fill plug without it running it will leak out very fast as the fluid that would be in the transmission system is now down in the pan, or at least a lot of it when the vehicle is not running. You want it to leak out a 2mm stream of fluid when it is running, and that is when it is full and you can put the plug back in the front side of the transmission pan. If it is dark brown or dark at all, it needs to be changed, and should be nice and red when you use new/fresh transmission (ATF) fluid.

YOU DO NOT want to get these two units (transmission vs. transfer case) respective lubricants mixed up!