Your track bars are what caused it, you either need adjustable track bars or track bar relocation brackets. The track bar centers the axle under the vehicle, one end attaches to the axle while the opposite end attaches to the frame, as you move the axle away from the frame it will cause it to shift to the side. Adjustable track bar or relocation brackets will correct this. Adjustable track bars would be the optimum choice as the brackets have been known to come loose.