Sorry if this is the wrong forum but I don't see a trailer forum so boats are the closest I could find.  Anyway I was going to pack the bearings on my new to me trailer this afternoon.  This is something that I'm very familiar with on a trailer with bolt on wheels.  But my trailer has the hubs and bearings built into the wheels.  I'm not sure how to go about setting the bearing preload.  I'll attach some photos do you guys can see what I've got.  I assume I need to set the preload with the larger inside nuts then attach it to the axle with the castle nuts on the outside.  The problem is that when I try it like that the whole spindle rotates with the castle nut and I can't get the nut tight.  Any help is appreciated

If the axle rotates it can change the load on the bearing that nut was set at. You have to hold one, and tighten the castle nut, I am guessing both ends of the axle have a castle nut? This only makes sense anyways as it is the only way to control bearing load on what I am seeing here. 

 

So you may need a thin jaw open end wrench to hold the inside, they do make them but you may not need it?  but while tightening the outer, the bearing nut will need to be heldgood luck. 

Thanks for your reply Capt.Bob.  I did get it back together I think my biggest problem was rust in the threads of the axel.  The castle nut would only go on so far then it would hit the rust and the axel would rotate with the nut.  A good dose of penetrating oil and some work with a wire brush got the threads cleaned out.  Then it all went together as expected.  I'll be investing in a angled to for my grease gun so next time I'll just pump it full of grease threw the grease zerk rather than taking the whole thing apart.