During initial setup, IIRC Dana used Crush sleeves to setup gear spacing(pinion depth). It takes between 300-400lbs torque to crush these sleeves. If shims are used, which is usually only if they've been rebuilt by a good shop, it won't matter. But if you can get yours off, when you put it back together, don't go much over 200lbs and you should be good. Pull the nut, thread seal, yoke, seal, install seal, wear sleeve(if needed), yoke, thread seal, and nut, and torque to around 200-250lbs, and you're good. I usually only go to 175-200ftlbs with the 3/4 impact gun and it's worked so far. I'm paranoid about the nut backing off the first few weeks, but it hasn't happened, yet. I did a Dana 80 last week, several others since the first of the year, and countles others this way. When you put it back together, see if the seal under the nut is all chewed up. If it is, try to find another or just "sillycone" the snot out of it. Not many people carry them. I get mine from
Randy's Ring & Pinion. The Differential Experts. Auto Parts & Services. My account manager is Ken Knudson, ext 5508, if you decide to order parts. I'll warn you, on the Dana 60, well, all of them, really, you'll probably have to use a light duty socket, as most impact sockets won't fit down into the yoke far enough to engage the shoulders on the nut. I've got a cheap set of Harbor Freight 3/4" sockets I use just for that... .
Oh, and you'll probably want a slide hammer to get the yoke off if it's been on there a while and been behind a Cummins, or gear puller, whatever you have.
Also, most parts house seals use a single lip seal, so I go with either the Dodge or get 'em from Randy's. Mentioning wear sleeves at the local store will get you a dumb look, usually. Also, check to make sure your vent tube isn't stopped up. I've fixed many wheel seal leaks by blowing it out and cleaning it up.
Attention: TDR Forum Junkies 
But, I've only put 5k miles on the truck.
