Since putting in the MS rear end with limited slip diff, I experienced bad tire wear with Open Country M\T's and with Wild Country XTX sport2. I have only done street driving, sad to say that, but after about 7k miles, both were\are at half tread or less. Fronts look brand new. the mt's were 255\85\16 and the xtx are 285\75\16. Les Schwab has no idea what's wrong because the wear is even on both sides. No cupping or anything. Oh, I do have a 6 degree shim under the springs too as I put in an add a leaf. Anyone else run into this?

Nope. Are you making hard or aggressive starts?

Two things to consider; One you're running an LSD and if you're not running an additive you will burn up tires, Two if you're axle swap is installed out of square you will burn up tires. Since you are running a stock axle with stock springs i'd suggest getting the LSD additive, you will loose some LSD performance offroad but there is a balance you need to achieve. More additive equals better onroad manners and less tire wear and less additive equals better offroad traction and worse onroad tire wear.

Check your rear axle for squareness with the front axle, get a friend and measure from a fixed point of the rear axle to the opposite side of a fixed point of the front axle. *Example: from the lower nut on the axle tube flange to the opposite side front LCA bolt, take the same measurement of the other sides (cross) the difference divided by .5 is how far out of square your rear axle is. I've seen up to 1/4" out of square on trucks that had no issues, leaf springs are pretty forgiving.

Your measurement will look like this

I just got back from Les Schwab and had it aligned because I turned down my torsion bars about an inch. Had them go over the rear and it checks out fine. So, I'll be getting some additive and giving that a shot. Thanks for the reply's.