Bryan, I took a steel plate and cut the oval hole with two flats in it with a torch, grind to fit good. then weld a big handle on it that you can slug with a sledge hammer. the problem is the hub slides onto a tapered splined shaft. as the splines wear a little, the hub comes loose. if you tighten the nut the hub moves in further than it was before. take the nut loose and clean threads. jack the tire up off the ground and then tighten the nut. see that the tire turns easily by hand. if the wheel gets tight as you tighten the nut, then the hub is bottoming out on the inside aginst the axle seal retainer because the tapered splines in the shaft are worn excessively. if this happens, remove the hub and grind 1/8 inch off the lip on back of the hub that is hitting the seal retainer and then reinstall the hub and tighten again, check easy to roll. of coures if the nut gets tight on the shaft and the hub is still loose, then you are right, you need to put a thicker washer on the shaft, under the nut. the washer should have a large enough center hole to slide freely