W900L leans to right

I believe the proper term for this lean is the 'Kenworth lean' caused by excessive power there is no cure

 

When you have a lean to one side and you inspect the front springs to axle mountings for equal spacing and you see a spacer on one side only, it could be that you're seeing the thick end of a tapered caster shim commonly used on just one side to manipulate the axle by twisting it when tightened down for desired caster setting. By adding a flat spacer to the low lean side, you can level the truck without affecting the caster setting as long as the tapered shim is left in it's original position.