Pinion Seal Replacement.

My method is to first get the truck / car parked or raised and secure where I can get under it. F-250, I'ld just back it up on my 8" ramps. Set parking brake and block front wheels .... don't need tire tracks on my shirt. Put trans in neutral, paint or punch mark driveshaft at rear yoke so it can go back same as removed, then remove driveshaft from rear axle at U-joint.

Now, I clean the exposed threads of the pinion shaft, the nut, the rear flange / yoke with wire brush if needed. Once clean, I take a sharp center punch and hammer and I punch mark ... the end of the pinion shaft ... the pinion nut ... and the yoke or flange.

I also measure the length of the threaded pinion shaft sticking out past the nut and count threads, and I write it down.

This way when time comes, I can put that yoke back on that shaft and tighten that nut back to exactly the same relationship ... and NO FURTHER. I do NOT want to compress any crush sleaves any further, I want to retain the exact same bearing clearences .... I just need a new seal wrapped around it all.

Now, I use a BFW and remove the nut and yoke and then pull the old seal and install a new seal (and if it's a lose fit inside the housing, you can use a locktite product on the outer side of the seal to fill voids but not on the lips) driving it straight in (not ****ed at an angle) ... lube it's lip ... slide yoke back on so it's punch mark is same relationship to that punch mark on the end or the shaft ... and then I slip the same nut back on with same side against yoke as it was when removed ... and apply some locktite on the threads.

I tighten it until close to original setting, then I sneak up to final setting so when I stop, the three punch marks are in the same relationship with each other and same length of shaft sticking out as when I started .... and NO FURTHER.

DO NOT GO TOO FAR.

I then .... if the nut was a loose fit, may take a punch and punch the threads of the pinion shaft in two spots just to make sure the nut doesn't loosen, though the locktite should prevent that .... and prevent any future sweating of oil that might work it's way out through the threads making it look like another leak.

But that's just my way. I've done it on my vehicles a few times over the years, even a couple police cars ... always sucessfully.

More:

The seepage on either side of the center casting at the axle tubes is not unusual. Those tubes are pressed in at the axle factory and retained by large puddled spot welds only. It is a tight fit, but with time, heat, cooling, stresses ..... seepage such as you see is not at all uncommon. You can use some 2+2 Instant Gum Cutter from NAPA, clean the joint area really well, wire brush it really well, then use some paintable silicone sealer and seal the outside and paint it like you would your houses window moldings if you like?

The crush washer has NOTHING to do with leakage.

The nut has NOTHING to do with leakage.

There is a good reason to NOT use a new nut or crush washer or other new part when simply replacing the seal itself. You should inspect the surface of the yoke where the seal rides and if not smooth, if pitted, get a sleave for it at NAPA .... but only if needed. It's possible that the seal was damaged by the installer.

If you change the crush sleeve or change the nut or change the yoke (companion flange, etc) or other part in the stack up, you esentially start from scratch setting bearing preload all over.