trying to figure out what is going on with my 01 1500 5.9 gasser. grinds in 4hi and 4low while under load, let off the accelerator and noise stops, more prominently while turning but does happen while going straight. removed front drive shaft and engage 4wd and no noise. inspected drive shaft u joints and both are fine, should i be looking into transfer case or front axle/differential first? thanks in advance!

 

Probably the chain in the t-case is stretched.