I have a few pinion seal installation PICS from my gear install. I had this posted on the 6.7L side, but I figured it might also help someone here.
First, mark and remove the front driveshaft then remove the unit bearings/axle shafts.
Next, rotate pinion gear 3-4 times then check and record rotational torque with axle shafts pulled.
Next, remove pinion flange nut and washer. If you dont have Miller Tool 8979, you can use a chain wrench or very large pipe wrench.
Next, remove pinion flange with Miller Tool 8992 or with a three bolt puller.
Next, remove the pinion seal with a pry tool. I gently tapped around the outside perimeter of the seal itself to remove the pinion seal.
Next, examine the pinion yoke seal surface for scrapes, gouges or roughness. If you find damage to the seal surface, replace the pinion yoke. Otherwise, clean the seal surface with a scotchbrite pad then wipe clean with a soft cotton rag and brake cleaner.
Next, install the new pinion seal with Miller Tool 8882 and C-4171 or a very large deep well socket or without the tool by using a piece of iron pipe of the appropriate diameter carefully tapping the seal a little at a time. Check the make sure the seal is going in squarely and is not ed.
Next, apply a light coat of teflon thread sealant to the pinion flange splines, and lightly tap the pinion flange on to the pinion gear. Install the pinion flange washer and a new pinion nut. Hold the flange with Miller Tool 8979 and tighten until the end play is taken up in the pinion.
Next, rotate the pinion 3-4 times to seat the bearings. Measure the pinion rotating torque and compare it to the recorded measurement taken earlier (in step 2). Tighten the pinion nut in small increments until the pinion rotating torque is 3-5 in./lbs. greater than the earlier recorded measurement (taken in step 2). Rotate the pinion one more time and re-check pinion rotating torque again. NOTE: this picture is the same one from step 2, and thus has the same recorded torque measurement. Your recorded torque measurement will want to be 3-5 in./lbs higher than your first recorded torque measurement taken in step 2.
IMPORTANT: If you overtighten the pinion nut and the pinion torque is much more than 5 in./lbs. over your initial recorded measurement(in step 2), you may have over crushed the crush sleeve. This will result in decreased pinion bearing life or pinion bearing failure. If this is the case, you will have to install an new crush sleeve on the pinion gear. That proceedure is a little more involved.
Last, reinstall axle shafts and unit bearings then reinstall front driveshaft taking care to realign reference marks.
One last note, some people will shortcut this proceedure by attempting to mark the pinion/pinion nut and/or counting the threads showing on the pinion and tightening the pinion nut to that point. Ultimately, the choice to utilize that method is yours. However, keep in mind that is not the recommended method, and may result in premature pinion bearing failure.