I need some clarification. The GM service manual says to pack the cavity between the seal lips of the pinion flange oil seal with lithium-base extreme pressure lubricant. It says in another step to pack the cavity between end of pinion splines and pinion flange with a non hardening sealer(such as Permatex Type A) prior to installing washer and nut on pinion.

Are these absolutely necessary and what exactly does it mean? Thanks.

Yes. If you don't lube the seal it might heat up and ruin the lip, causing a leak. If you don't seal the splines in the yoke then oil will leak through the splines and around the pinion nut.

So where does each one go?

Just smear some oil or grease around the rubber lip of the seal. Smear some RTV into the splines of the yoke before you put it on. Don't put any sealer on the splines of the pinion shaft because the yoke will shove it into the outer bearing.

Ok so put RTV on the yoke splines and lithium grease on the part of the seal that the pinion shaft spins in, correct?

Yes.

My only remaining issue is with the yoke nut. Before removing it, I got a reading of 2.5ftlbs. to turn it. Does that seem like a low number? I put it back to that, but that sounds aweful low. I read in the manual for a used pinion bearing, it should be 5-15inlbs. I set it back to EXACTLY what I got when I took the initial measurement. It was set up to 2.5ftlbs. What do I do? Even 2.5ftlbs sounds VERY VERY loose.

I just torque the nut to 150 foot pounds and use red Locktite on the threads. It's a good idea to use a new pinion nut. If I use an old nut I put it in a vice and hit the edge in a ferw places with a ball peen hammer to restore the lock feature of the nut.

You use 150ftlbs? The GM manual says for a brand new nut 20-25 INCH POUNDS. I did get a new nut also.

That's bearing preload, not torque on the nut. You set the bearing preload to 19 to 22 inch pounds when setting it up with new bearings. For used bearings it 5 to 10 inch pounds. That has nothing to do with torque on the nut. If you are just changing the seal and not disassembling the rear end then just torque the nut to 150 foot pounds and don't worry about it. If you have the rear end apart then check the preload on the bearings and set it to about 5 inch pounds and torque the nut to whatever it takes to set the preload correctly.

I am confused because the nut is what sets preload on the front pinion bearing, isn't it? If not, then how because my rear only has the one nut that holds the pinion yoke on. I had the pinion bearing out to look at it and after I pulled the seal out, the bearing nearly fell out in my hand.

The GM service manual doesn't say anything about torquing the pinion yoke nut to 150ftlbs. In fact, it says to torque it to the same reading you took with your torque wrench before you removed it.

Here is what HotRod Magazine says about pinion bearing preload:

Preload must be checked with an in-lbs torque wrench. Most in-lbs wrenches start measuring at 20 in-lbs, but the correct preload on a 12-bolt is 17 to 18 in-lbs, so we had to step up to this wrench from Snap-On. Take the reading as the wrench is turned through a gentle arc and not as soon as you start turning it. The breakaway reading will be much higher than the true preload reading.

Everywhere I look, it says 18-20INLBS. Nowhere do I see anything about foot pounds. Here is another article on pinion bearing preload:

After reading some additional posts and articles, let me try to figure this out. When the book says bearing preload, they are referring to the rotational force needed to turn the pinion? My GM manual says 5-15inlbs for a used pinion bearing. That means after the pinion yoke nut is finished being tightened, you should be able to place your inlb torque wrench on the nut and get a reading between 5-15inlbs to turn the pinion nut around AFTER the initial break loose, correct? The 5-15inlbs IS NOT the torque for the nut, but the amount of torque it requires to turn the pinion nut AFTER all is said and done, correct?

Yes, that is correct. There is a spacer between the inner and outer pinion bearings. This spacer holds the bearings apart. The spacer is designed to crush when you put enough torque on the pinion nut. You tighten the pinion nut until the spacer crushes enough so that the bearings make contact with their races. At this point you tighten the nut in VERY small incraments so that the bearings are preloaded against their races and will have some resistance to rotation. This is bearing preload and it is measured in inch pounds. Preload has nothing to do with pinion nut torque. When the spacer has been crushed and you have to loosen the nut to replace the pinion seal or yoke then the spacer will not return to it's original length. When you reassemble everything the spacer will already be crushed and the bearing preload should remain the same when the nut it tightened, as long as too much torque is not applied to the nut so that the spacer is crushed more. If this happens then the preload will be too much and the rear end must be disassembled so that the spacer can be replaced and the preload must be set all over again. I have found that 150n foot pounds of torque on the pinion nut is enough to hold everything tight, but not increase the bearing preload. I use a new nut and red Locktite on the threads to be sure that the nut doesn't back off later.

Does this inch-pounds measurement apply ONLY if you have no carrier in place? In other words, just the pinion nut, gear and pinion bearing you are measuring for 5-15 in/lbs?

I don't understand how you could measure anything in inch pounds if the pinion gear is contacting the ring gear...

I ask because I have this job ahead of me also.
Thanks BGH.

You are correct. If you are measuring the pinion bearing preload the only thing that can be installed in the housing is the pinion. Everything else must be reomved. When checking used bearings I prefer to stay on the loose side, closer to 5 inch pounds.