Well I think we found the problem. After almost 2 hours of messing with his center diff, we used a new diff housing, all new internal gears and it would still lock up in your hand, we even put 3 thick gaskets on the ring gear and it still locked, like it was really stiff. I took it apart myself the last time to look at it and I found the large washers behind the crown gears are mis-machined. They are thick as hell. If you put about 5 regular large shims together it would equal one of these shims. Both were like that. Just trying to break the diff in with drill it got very hot before. Now the Diff is nice and smooth and spins really free.
Will see wed. when he practices. I removed the center Diffs on my 2 K8T's and they felt exactly the same so I think he will be fine.