Is it possible someoine replaced that hub at one time ? If you look at bearing buddy website ,you will find that there are different diameters for different brands of hubs . They list 1.781 " , 1.810 " and 1.980 " . You may need the 1.810 instead of the 1.781' . That's not a big difference in size ,but could account for your lost caps . If you have an inside micrometer you could measure the hub .