I have a 2004 Mountaineer Premier AWD, 4.6L. The previous owner had removed the front drive axels as they had some kind of sound they couldn't identify the origin. They left the transfer case intact.

Not long after I had it, the transmission went out. i tried all sorts of fixes that failed. It needed to be replaced or rebuilt.

After reading a kazillion forums and comments, I was resigned to the fact that I was going to need to not only do the transmission replacement or repair, but that I would need to replace the front drive axle system as well. Not doing so would invite damage to the transmission again.

I was told that if I were to try and make it a RWD, I would need to replace the rear drive shaft with a custom welded unit and would need to flash the computer.

WRONG. NADA. NOPE!

I did replace the transmission with a rebuilt one, removed the transfer case altogether and replaced the rear drive shaft with one from a RWD. All matched up and going strong now over 6 months!

Thought this might be helpful!