The only shim adjustment I know of on these gearboxes is for the worm gear bearing pre-load, which only affects the amount of pressure the end-cap forces the bearings against the worm gear bearing races. If there's too few shims (increases bearing pre-load), it makes the steering wheel harder to turn, while at the same time you might still have sloppy steering due to some other malady mentioned by the good folks above. If there's too many shims (decreases bearing pre-load), it leaves a small gap between the bearings and races, but wouldn't really have an affect in causing sloppy steering unless you had a really substantial gap in there. If I remember right, the available shims come in three thicknesses and they are paper thin to less than paper thin, so if you had NO shims at all, I don't think it would have a substantial effect in adding to steering slop. Either way, having too much bearing pre-load or not enough bearing pre-load would probably eventually ruin the bearings. I believe you want to shoot for about 5/8 inch lbs torque measured at the end of the steering wheel spoke near the rim.