Final drive idler sprocket set up.

[newday]

Im checking/setting the bearing clearance/preload on the chain idler sprockets on a Thomas 243HD. The repair manual says to tighten the castle nut on the preload bolt that is outside of the final drive housing until there is no clearance. Im finding that it is hard to isolate that movement with the chains hanging on the sprockets, plus trying to get prybars on opposite sides of the sprocket to rock things back and forth with any reliability is difficult. So when I put a dial indicator between the large sprocket and the outer housing I find that it the reading decreases when tightening the castle nut on the preload bolt. So I put the dial between the outer housing at the access door right above the bearing outer flange and touched down on the inside of the inner housing. When I tighten the preload bolt the distance between the inner and outer housing decreases with minimal effort on the wrench. Once the dial stops moving I can instantly feel more resistance on the castle nut. My assumption is that when the dial stops moving the tapered bearings are at roughly zero clearance. The manual has no details other than tighten castle nut until there is no play. Im wondering if anyone has some experience or insight on a procedure for this. I tightened the nut until the dial indicator needle stopped and then put the cotter pin in. Or went to the next tighter if the hole was not lined up for the cotter pin. Im thinking that it should actually be a little tighter than this given the low rpm and high load. Any comments or guidance would be very much appreciated.