Originally Posted by Skotter
Do a search for "castor" and there's a comprehensive write up on it (might even be sticky, not sure). I'd stay away from shims. Generally, they're either going to negatively affect your castor or your pinion angle. Might help one, but it's going to hurt the other.
That's true especially when you consider that stock caster agnle from the factory is 3 degress +1 (4 degrees?). Mine was only 2 degrees and I added in 4 degree steel shims for a total of 6 degrees positive. Drives and handles excellently. As you say, the compromise is in the front U joint angle but I normally run with my hubs free anyway and seldom exceed 20 MPH in 4WD. I run a 2" lift with my skid plate lowered 5/8" to correct rear U joint angles. I've noticed that with this setup, there is a barely noticeable angle at the front pinion U joint. If I really wanted to run with my front hubs locked on the highway, a CV joint could be used at the transfer case front output assuming that there is enough room at the skid plate to accomodate the bulk of the CV .