Popping noise in 4wd under load

[Troyfast04tj]

I have 04 sport 4.0 with 5 speed. Changed DS in front and replaced u joints in rear.
Still does it. I jacked up one front tire, Jeep in 4wd trans in neutral. Spun front tire and tcase made this noise. Would it be chain issue ?

 

[Jerry Bransford]

A stretched chain was the first thing occurred to me too.