Another question related to my "new" 8.25 SG rear end. When I got the rear end home from the yard, the entire top of the gear case was covered with a thick (over 1/8"?) layer of dirty grease. The inner third of each axle housing was also covered. When I drained the fluid out, it looked like pancake syrup and flowed like molasses (that's good, right?), but I only got about a quart out, where it should have been filled to 4.4 pints (2.2 qts). The greasy exterior and the low fluid level makes me suspect a leaky pinion seal. ***Does that sound right?*** I was going to drop this rear in without replacing any seals, but now I wonder if I should replace the pinion seal while the assembly is sitting on jack stands on the garage floor. Based on reading the FSM and what I can find on the web, I think I can use the following procedure to replace the seal without messing with the bearings or the crush spacer:

1. Use an inch-pound torque wrench on the pinion nut to measure the torque required to rotate the differential (the axles are not installed right now but I don't think that should matter?). This torque is the "pinion bearing preload" measurement.
2. Use a big-ass wrench to hold the yoke in place while backing off the pinion nut.
3. With the pinion nut and washer removed, remove the yoke ("drive pinion flange" per FSM). ***The FSM shows some special tools for this: can I do it without them? How? ***
4. With the yoke removed, pop the seal out with a screwdriver. Replace with a new one, leaving the old bearing in place so as not to mess with the old crush spacer. ***Is it a bad idea to leave the crush spacer?***
5. Reinstall the pinion washer and nut, tightening it gradually until the previous bearing preload is attained. (It should take about 210 ft-lb, but my torque wrench only goes to 150 ft-lb. I'll just have to make sure it's greater than 150.)

Does this make sense?

Let me re-ask the specific questions from my perhaps over-long post.
1. If the top of the pumpkin is covered with crud, does that suggest the pinion seal is leaking?
2. Do I need the special tools shown in the FSM to remove the yoke (drive pinion flange)?
3. Is it a bad idea to leave the old crush sleeve in place? FSM mandates a new one.
4. Do I understand correctly that the "bearing preload" is the amount of torque required to rotate the differential before I remove the nut?

A 1969 Chrysler video shows how to replace the seal without replacing the crush spacer and front bearing (skip to 13:27). I'm documenting the steps here, as much for me as anyone else, but maybe it will help someone. Steps:

1. With the wheels removed, measure and record the torque needed to turn the pinion.
2. Remove the pinion nut.
3. Mark the splines on the pinion and the flange (yoke) to be sure to put them back the same way.
4. Remove the flange.
5. Inspect the splines on the pinion and the flange for nicks and burrs. Inspect the journal surface on the flange. Replace if rough or grooved, even if grooves are smooth.
6. Remove seal and install new seal. No sealer (RTV) is necessary. *Edit: 1974 shop manual says sealer is necessary on the 8.75" diff but not the 8.25 or 7.25.
7. Replace flange with splines oriented the same as before.
8. Torque the flange nut to 210 ft-lbs. *Edit: video says 170 ft-lbs, but 1974 shop manual says 210 ft-lbs.
9. Check pinion turning torque. If 0 to 10 in-lbs greater than before removal, you have over-crushed the crush spacer and you have to replace it and the front bearing. *Edit: video says up to 5 in-lbs, but 1974 shop manual says up to 10 in-lbs.

To answer my own previous questions: Probably. Not necessarily, as long as I have a way to hold the yoke from turning while turning the nut. Once the nut is off, the yoke should just slide out. If you remove the bearing, you have to replace the crush sleeve. If you leave the bearing in place, you don't need to replace the crush sleeve. The pinion turning torque is directly related to the bearing preload and is the way to set/check it.

Feel the rotating resistance now . remove nut with impact. Remove yoke you might need to hammer it then sand seal surface with #400 to polish it up. Remove old seal. Grease up seal surface and pack the ba k of seal with grease and install. Then aply lock tight to pinion threads and tighten slowly and check for play tighten till you can feel the slightest play just to note your almost done tighten till all lay is gone and to lslight resistance to turn pinion.

The problem I'm running into now is the turning torque is not constant--as the pinion turns the torque ranges from about 3.5 in-lbs to about 7 in-lbs. This variation happens at the same yoke positions every time, so the rub must be in the pinion or its bearings, or the yoke, or the seal. I'd like to just go ahead and replace the seal to see if that fixes it, but then what pinion turning torque do I shoot for, when I don't have a reliable measurement of the existing torque?

There's another issue that may or may not be related. As I rotate the pinion there's a hard catch every once in a while. It feels like debris in the gears, even though I don't see anything. After passing the catch, going back and forth doesn't reproduce it. But it eventually shows up again. When I get time I plan to flush the ring and pinion gears and see if the catch goes away.

Flush it all out and check it then if it still caches like that I would pull it apart may have a bad bearing. Does it feel smooth other than catches or is it rough if its smooth its Likely dirt in pinion beari g or in pinion gear teeth turn till a catch and see if you still have backlash if down gear is tight then its dirt or dinged tooth

I read your post again noticed you said the catch doesn't reproduce so it is likely a bad bearing or dirt in a bearing

I flushed out the gears with motor oil, and the hard catch went away. Must have been some debris in there. Also, the uneven turning torque only happens when the differential is upside-down. I didn't think the orientation would make a difference, but the turning torque is pretty steady at 3 in-lbs when the differential isn't upside down. I've replaced the seal, torqued the nut to the same preload as before, and will update again once I get this rear installed and running.