Jeep only works in 4x4?

[exile00]

Im very new to jeeps i just bought a 1980 CJ5 , it was working fine, then one day i heard a loud snap while driving, and now it only drives in 4x4? any idea what that could be?

 

[JR74CJ5]

That sound like a blown rear end but youd hear clunking while driving id assume... Could it be in the Transfer Case ?

Put it on stands and see if rear drivling is turning when in gear though i still think youd hear a clunking...

 

[coldair]

Sound like you that you stripped a rear drive hub. You prob have a stock AMC20 rear. I would look there.