03zr2 transfer case poping in 4x4

i just bought a 03 zr2 s10 4x4 with 96,000 miles on it,and when u have it in 4wd in make a loud poping/clunking noise from the transfer case! front wheels are pulling! ingages in both 4wd low and high! when u put it back in twd the light indacates its in 2wd and it clonks once more and then its fine until u put it in 4wd agin! i have changed the case fluid out but its still doing it! any ideas? thanks every one!!

i just bought a 03 zr2 s10 4x4 with 96,000 miles on it,and when u have it in 4wd in make a loud poping/clunking noise from the transfer case! front wheels are pulling! ingages in both 4wd low and high! when u put it back in twd the light indacates its in 2wd and it clonks once more and then its fine until u put it in 4wd agin! i have changed the case fluid out but its still doing it! any ideas? thanks every one!!

What transfer case and transmission?
Did you use the right fluid?

I would check all axel and drive line joints and splines and mounts and also look for loose transmission to engine or transfer case to trsansmission mounting.