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After finishing some yard work this morning I found some time to replace the leaky pinion seal on the rear end of the IROC. It'd been leaking for a while, as it was a mess under there.............
Next I marked the drive shaft, so I could be sure to get it back in the way it came out, I then removed the drive shaft and torque bar to gain access to the pinion nut. I counted the number of threads showing on the pinion shaft for reference during the reinstallation of the nut.
I then removed the pinion nut and yoke to gain access to the leaky seal.
I then pried out the old seal and prepped the new seal for installation. I used a small bead of RTV sealant around the metal to metal portion of the seal and lubed the rubber portion with a dab of gear lube, to prevent it from burning up before lube can get to it on the initial drive after the install.
Next I installed the new seal by lightly tapping it in, working around the seal evenly until it’s seated.
I then reinstalled the yoke on the pinion shaft, in the same position as it was removed. I applied a small amount of RTV sealant on the splines of the yoke, to prevent any gear lube from leaking through them. Next, after applying some red thread lock to the nut, I installed and torqued it to 150 Foot LBs. I then made sure that I had the same number of threads showing as I did before removing it.
It takes around 200 Foot lbs of torque to crush the pinion spacer on a GM 10 Bolt, so in theory, if you torque to 150 or so foot lbs and have the same number of threads, your pinion depth has not been changed; it's always worked for me through the years anyway.
And finally, I reinstalled the drive shaft and torque Bar, then topped off the gear lube. No more oil drips in the carport!
You forgot the new crush sleeve. It's mandatory. And it's not by ft/lbs, It's by rotational drag with no lube in there. If you can afford the seal, then you can afford new lube, a new gasket, a new crush sleeve, and a new pinion nut, which is also mandatory.
It's really irresponsible to do a how-to if you're going to do it wrong. You might get away with it, but if the next guy doesn't, then you cost him a lot of time, money, and anger that you have no right to cost him.
You don't have to change the crush spacer if you are just replacing the seal or a yoke. If you were replacing a bearing then it would be required to change the crush spacer and check the bearing preload. If you are not replacing the bearings then the crush spacer thickness doesn't need to change. If you torque the pinion nut to 150 foot pounds it's tight enough to hold everything in place, but not tight enough to change the bearing preload. I've done this many times and I've checked the bearing preload on a few to be sure that it doesn't change and it works fine. There is no need to completely disassemble the rear end just to change the pinion seal or yoke.
You forgot the new crush sleeve. It's mandatory. And it's not by ft/lbs, It's by rotational drag with no lube in there. If you can afford the seal, then you can afford new lube, a new gasket, a new crush sleeve, and a new pinion nut, which is also mandatory.
It's really irresponsible to do a how-to if you're going to do it wrong. You might get away with it, but if the next guy doesn't, then you cost him a lot of time, money, and anger that you have no right to cost him.
With all due respect, it's not a 'how to', it's more of a 'how I did'. I've been a professional mechanic for about 30 years now and have changed many pinion seals this way. The fluid was not changed because this fall the gears are getting swapped for a posi unit with 3.73 gears, but thanks for mentioning it, I usually do change the fluid too when doing this task.
Add me to the list of guys who've done them the same way as this write-up, many times, with no problems. The only time you have a problem with the old crush sleeve is if you over-tighten it and end up crushing it further. Also, provided the threads are in good shape, it's no problem re-using a pinion nut either. I always put some red Loctite on it to make sure it won't be backing off. Most manuals will tell you NOT to re-use the nut, but you can, provided it's in decent shape. I have to add, I've eliminated the problem of the crush sleeve on most of my new rearend builds by using a solid pinion spacer instead of a crush sleeve. It's a stronger setup, and makes replacing a pinion seal or yoke a breeze.
Add me to the list of guys who've done them the same way as this write-up, many times, with no problems. The only time you have a problem with the old crush sleeve is if you over-tighten it and end up crushing it further. Also, provided the threads are in good shape, it's no problem re-using a pinion nut either. I always put some red Loctite on it to make sure it won't be backing off. Most manuals will tell you NOT to re-use the nut, but you can, provided it's in decent shape. I have to add, I've eliminated the problem of the crush sleeve on most of my new rearend builds by using a solid pinion spacer instead of a crush sleeve. It's a stronger setup, and makes replacing a pinion seal or yoke a breeze. 
