When I bought my truck (2001 F-150 4x4) back in December it had relatively new tires on it. The inspection needed a couple parts replaced which required an alignment. Got that done along with rotation and balance.

When I turn from a stand still, it sounded like the rear tires were gripping a little instead of turning (hope that makes sense). I didn't pay too much attention to it until I noticed that the outside of both rear tires are wearing much faster than the rest of the tire (noticeable with only 5000 miles since the alignment). I jacked the rear end up and tried shaking the tire but it was on the axle solid. I decided to change the brakes while I had it jacked up. New pads and turned the rotors and now there is not "gripping" sound when I turn. Could brakes cause this gripping sounds, and hopefully be the reason for uneven wear?

 

If they were dragging it would add to the wear.
If your truck has posi traction, that will cause the inside tire to sprag on sharp turns as well. This is normal condition.
Posi traction is a an internal clutch stack that must slip on sharp turns or anytime the truck is not moving in a straight line.
If the surface has gravel/dirt, hot surface etc you may even hear a short squeel from one tire.
Good luck.

 

if the noise only happens when turning, then its probably not the brake shoes, right ? The axle might have an LS (limit slip unit) which is what bluegrass describes above. You can go to Auto Zone and get a 7 oz tube of "friction modifier" and pour into the rear axle and that will fix the clutch plates.

 

I need to jump in here and say a word about additive.
The clutch packs when run in fluid with 'no' additive will sprag (max friction) the max amount.
The additive is to reduce the clutch 'hook-up' friction to a reasonable level consistant with the intended use of traction lock..
If you add more than the specified amount, the clutch will not be as effective as it should be for traction and slip an eccessive amount (one wheel spin).
If the rear has no additive, add only one container.
If it has it in, do not add anymore.
There is sometimes a mistaken belief that more additive clears a fault but may make the traction lock nearly useless for what it is intended to do.
If you don't know what you have, replace the fluid and do the additive so you know what you have, then see how it goes.
Could be the clutch discs are worn or are good.
Good luck.