Replacing a pinion seal is no big deal, IF you get the flange nut torqued right after the seal is installed. There should be a little bit of bearing preload when the job is done, a drag as the pinion is turned. I usually check the load with an inch-pound torque wrench before disassembly, and try to dupilcate it when I retighten the pinion nut after installing the new seal. If there's NO drag, it probably means you've got a bearing in the process of failing, and it needs to be replaced or the seal job won't last long. That gets into some definitely precision setup, as the pinion gear has to be removed, both bearings replaced, and the preload has to be set from scratch. If there's any front-to-back movement of the pinion flange, you're in for a bearing replacement, not just a seal. Take the job to a pro with the right equipment in that case!
Jerry
