Just something to think about, since the work was done at a Ford dealer, I guarantee they used the motorcraft gear oil used from the factory... Not saying it is "bad" stuff, but we have all seen what it can potentially look like after 30k miles. You might want to get in there and change it out with something more tried and true before it starts to burn and gum up again! I have done quite a bit of reading on the subject and it seems that Amsoil Extreme Gear Oil scores highest consistently in the areas that our PTU's need (burn resistant, high pressure loads).
I just changed my PTU oil out and replaced it with the motorcraft stuff, but on my next oil change Im going to do it again with amsoil, just giving it a chance to dissolve some of the gunk and delute the crud so I can get as much out before putting the good stuff in!