Blown Seal, What Do You Think?

[BBarger]

My son was driving on the highway when he had a lot of smoke come out the back left side of my 1999 GMC Suburban. When I got it home and looked underneath it looked like the rear yoke seal where it attaches to the driveshaft had blown, spewing rear end fluid all over the place including the tail paipe/muffler, which is what must have caused the smoke. We've got about 120,000 miles on the truck so I'm thinking it's just a seal, any ideas? I don't really want to change out the pinion yoke bearing unless I absolutely have to.

[8.1HD/ALLISON]

Shouldn't need to change the yoke unless its all scored up.