If the '46 1-1/2 ton rear axle is the same as the later ones (and I'd be surprised if it isn't), the pinion is mounted with ball bearings and there's no adjustment, shims, or crush sleeve. The forward pinion bearing is a double row ball bearing, and it has a second ball bearing behind the gear. Everything is held together by a bolt-on bearing and seal retainer. All the adjustment is with the ring gear carrier bearings, so if you don't mess with that, it should be fine.
So it should be a piece of cake (relatively) to replace the seal. Remove the pinion flange, remove the bearing/seal retainer, drive the seal out of it, and drive in a new seal. Bolt the retainer back in place (pay attention to the gasket thickness), install the pinion flange and tighten the nut back on. The 47-54 service manual calls for 160-280 ft-lb of torque on the nut. That might be the hardest part. You'll probably need a flange holding tool to get that much torque on the nut. I would recommend NOT using an impact wrench.
