Assuming this is a narrow front? There are several things that contribute. The u-joint on the steering shaft may be worn and loose, The pins on both ends of the U-joint that hold it to the shaft can be worn, loose etc. The worm/pinion meshing in the steering gear box (under the plate up front) may be too loose. This can be adjusted some but on mine, with everything else tight, I found I had to remove some of the shim's which allow the worm to better mesh with the pinion gear. Originally there was no wobble to the steering on these tractors. I never had to replace any bearings, just the U-joint pins and remove a couple of shims and mine is like new, no wobble at all.