Rear Axil Seal - Inner and Outer

i had the same problem with the axle fluid leaking into the drum, but i didnt have the same bad luck as you. i replaced the inner seal myself, the outer seal had to be changed at the dealership because of the need for a puller. if you have ABS they get you every time with that too because apparently the little gear before the outer seal has to be cut off and replaced with a new one, it cant simply be pulled off. if you have your truck worked on at a dealership and it didnt get fixed, i would take it back to them and say you paid to have it fixed, and its not fixed. somebody at that dealership needs to fix your leak even if it means getting you a new rear axle. see what they have to say about that good luck with the leak tho hope you can get them to fix it for no more cost to you

Silly question, but have you checked the breather?

When the rear axle warms up from driving (and it does!), the oil and air in the axle expand. If the breather is plugged, the expansion will push oil past one of the seals (can also be teh pinion seal if you're lucky), no matter how good they may be. And the average "professional" mechanic (from personal experience) does not check this as a possible cause when he changes the seal. This happened with my Dad's Winnibego (of all things). Two sets of brake shoes later.... he asked me to take a look.

Just my 2 cents.
D'mon