My bad… I was thinking about it all wrong. You’re correct. Please go with what he stated I was thinking about it backwards.Shims installed with the thick part forward will increase positive caster and typically track better. Thick part to the back will increase negative caster and will increase wander and twitchiness. I agree with crusiermatt, looks like there's 1 frt spring and 1 rear sping on the frt and the same on back.
What you experienced is the same result as roll steer. During roll steer, the axle does not stay perpendicular to the centerline of the vehicle as the vehicle rolls and suspension articulates and it induces “steering “ without any steering input. Youre axles were likely not perpendicular to the chassis due to differneces in length from fixed end of spring to the center pin being different left to right.Thanks everyone just about finished the swap out last night, will let you know how it goes.