So you are missing a thrust bearing.... I bet the axle and spindle is junk. I've seen a 1/2 ton that had locked up (no grease) thrust bearings and the bottom side of the axle and the spindle too were worn so bad it was a lost cause.
Clean it and have a look before you fight with it any more, see if it's worth the fight or if you're in search of a better axle.
The hard part you hit with your drill is the kingpin, you won't have any luck drilling it.
Grigg
