That sounds like the rear main seal. You can drop the oil pan to get to the seal without dropping the tranny. When you put the new seal back in, make sure you keep your fingers off of it, I used gloves, and don't force it. I used some motor oil to lube it before inserting back into it's spot. It's a two piece seal. Put the top half in, use a plastic zip tie to get it started. Put the zip tie smooth end against the metal sharp portion of the tranny to gently guide it in, Then gently push it around and up with your finger. make sure you notice how the old seal was oriented when you took it out. Put the new one back the same way. Then put the bottom seal in the pan. Put new seal around oil pan (good time to clean it out and repaint, but don't get too agressive cleaning up the solid particles on the bottom end of the motor. You can loosen a bunch of crap up in there that you won't be able to get back out. Change the iol after the first couple hundred miles anyway after replacing the seal.), put some RTV black on there and bolt it back up. Put bolts in, then tighten a little at a time criss crossing to evenly distribut load.
After about 200 miles, change the oil and re-check oil pan bolts.
Mine leaked like a sieve when I got it, and burned on the exhaust. After replacing the seal, no more leaks, and no burning smokey smells.
The other thing that can leak and smell is the oil pan drain bolt. I had to rplace mine.
If your rear main has been leaking for a while, make sure you check the transfer case mount. They deteriorate quickly being soaked with oil.
