well why not do a proper diagnosis instead of shotgunning it.[throwing parts at it].Get it in the air all 4 wheels, start it and put it in drive. Now listen for the noise.is it there? If no put it in 4wh. Is the noise there? If you here the noise try to isolate it. I use a stethoscope.a long screwdriver works good to. Put one end on the part the other up to you're ear tight and listen. Put the screw driver on the closest to the noise NON MOVING PART. Then move say 6" away. Is it louder or not? If you hear it at the trans or rear diff listen on both sides as it will travel. And narrow it down. A very abbreviated diag formula. Hope it helps.