Pinion seal

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No the crush spacer, new nut, and new washer all have to be bought separately. The pinion nut has to be torqued to 175 ft-lbs to achieve the required preload. The preload spec is 8 to 14 inch pounds (with used bearings).

 
+1 with Don if the the rear end is apart.  If still together it will be hard to gauge the preload.  You have two option if so.   Pull just the pinion and follow the torque specs as Don mentioned or if you want you can leave the pinion in and mark the threads right where the nut is at and then remove the nut and replace just the seal.  Make sure that your mark is easily visible.  I would get a new nut and then tighten it down to the marks you made and then just a smidge - like one degree more.  If you over shot your mark you could add to much preload and crush the spacer a little more.  You can never back the nut off.  If you do you could be allowing play in the pinion throwing off the backlash causing whine and excessive gear wear.    

 
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If it's in the car, the procedure is basically the same, the only difference is that you must measure the preload before removing the pinion nut. After installing the new crush spacer and seal tighten the pinion nut until you get to the original preload, then tighten the nut some more until you get an additional 8 to 14 inch-pounds above the original. It will require around 175 ft-lbs, so you will need the proper equipment. You will need something to hold the u-Joint flange while both removing and installing the pinion nut, to keep it from turning, you cannot apply the parking brake strong enough to keep it from turning. I have a 3-foot long pipe wrench that I use.

 
I’ll give you my $.02.  Don’t replace the pinion seal without an inch pound dial or beam style torque wrench.  It is the only way to accurately measure preload.  Too little or too much preload = failure.

With the right tools in hand it isn’t that bad of a job to do. 

1/4” drive 0-30 to 0-75 inch pound range dial or beam type torque wrench, with drive adapters connect it to a 1/2” drive socket.
 

1/2” drive breaker bar and appropriate socket for pinion nut.

large pipe wrench or home made fixture to hold yoke.

2 jaw puller

Hammer and seal driver

Here is how I would do it.

With the car safely supported, parking brake off and wheels in the air I would use the inch pound torque wrench to measure how much force it takes to rotate the pinion.  Just slowly rotate it, one rotation every 2-3 seconds, and record how much force it takes to maintain rotation.  Say that number is 4 inch pounds- 

Now get out the pipe wrench to hold the yoke and breaker bar to remove the pinion nut.  Remove the yoke and seal.  Clean the threads and splines well, taking care not to launch dirt into the bearing.  
 

Install new seal.

Use a sealer on the splines, and a thread locking compound on the threads.

Install the yoke and pinion nut.

Tighten the pinion nut until you have some resistance, then tighten it in very small increments (like 10 degrees), alternating between tightening it and measuring how much force it takes to rotate it.  You will find that it does not take much to radically change the preload.  So say you tighten it up and check preload, it measures 2 inch pounds, so you tighten the nut 10 degrees and measure again, this time you measure 8 inch pounds.  I’d call that good.  If you were to tighten it another 10 degrees you may overshoot.  Once you overshoot you have to replace the crush sleeve and start all over.

When you R&R the seal only on a crush sleeve style pinion you shoot for an ending preload that falls within specification for used bearings, but is also at least a few inch pounds above your pre disassembly measured preload.

The idea is to put it back together at a slightly higher preload so that you crush the crush sleeve slightly more, but keep it in spec.

Hope that helps.  If nothing else it justifies a new tool purchase.  The CDI brand torque wrenches are a decent value, the bodies are plastic, but they seem accurate.

 
As suggested . mark the nut prior to removal , retighten up to just past the marks is the safest 

 
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