If I am understanding you. You are going to replace the seal without replacing the crush sleeve. I am by no means an expert in this but, I would not do this. I have a shimed crush sleeve in mine and you can do it as long as you set the in lbs correct. I would take it apart and do it the right way.
The correct way is to replace the crush sleeve every time you unload the pinion nut. Some guys remove the crush sleeve, slide it onto a round pipe or used pinion and beat the crush with a hammer to extend the length so it can be reused, but that's not the correct procedure either. Some guys ,like baracuda pointed out, install a shim under the crush sleeve and reuse.
Just know this, if you don't take steps to place the proper preload on the pinion bearings with the crush sleeve, the tourqe applied to the pinion nut will place an abnmormal load on the bearings and bearing failure may result.
On the other hand, millions of mechanics have replaced the seals without ever messin' with the sleeve and without bearing failure.
Be aware that the rotational torque on used bearings is different from new bearings. Good luck and use an inch pound torque wrench to finish.
you could go ahead and install one of those solid crush sleeves, then use shims to get the right preload, or just get a new factory style crush sleeve. Either way, do it right and by the book, replacing the bearings and/or the ring and pinion is a pain in the rear (no pun intended) and it aint exactly cheap either. good luck!!
I use a 10" channel 5 foot long,,than I cut a notch to just fit the yoke in,I get a breaker bar and a pipe about 4foot long then I stand on the channel it takes about 375# to crush that sleeve,I think that I left .008 clearence.you crush it very slow if you go to much you have to cut it off. -0*(