My chevy z71 1994 model has been making a grinding

Sounds like your rear end may be going out, check your diff.

grease ur differential ur rear end get underneath find all ur grease zerts and ask a shop how to grease ur rear end

be looking at all the drive components back there..look for broken drive train issues and maybe bad suspension stuff..

Check drive shaft assembly for worn u-joints.if OK check for worn pinion bearings or loose pinion nut.This can all be check shaking drive shaft at each end and looking for slop in u-joints or pinion flange.

sounds like wheel bearing to me

It is the transfer case. It seems to be a big problem with the 2004 and 2005 models. They are not synchronized and bend the forks alot. The noise you hear is the chain rolling off the gear. Mine only did it when I was going over 45 downhill and not on the throttle for a few seconds. Hope this helps...

universal joints or rear end

You say 'new' truck, 09? or new used? I have had 3 Fords, 3 w/ manual trans. case, if you go into 4x4 Low range, you must come to a complete stop before shifting the trans. case to 4x4 mode, and I always put trans (automatic) in neutral before slipping into 4x4, it engages smoothly, no grinding. 4x4 high range can be put in while moving, but I would let off the gas pedal, shift to 4x4 high range, then resume accelerating. If there is any grinding going on doing it as above, something isn't right. Check the trans. case fluid level also, to make sure that's not an issue.

sounds like the power sterring pump check valve is failing because it only when you turn, try to turn the wheels standing still to verify the noise, if noise present, replace the ps pump.

This sounds like the famous problem that those ten bolts give, remove the rear differential cover and inspect the oil for metal debris, it's more than likely to be the carrier bearings wornout making the ring and pinion offmesh causing the grinding and will eventually break. Hope this helps