Rear suspension

I grabbed the pinion yoke and couldn't get it to move sideways or up-down, but forgot to try pulling outward on it.

The hunt continues, I guess...

The oil was pretty black and smelled like gear oil does, but I didn't see much if any metal in it. But the new pumpkin was one complete unit, the whole third member, ready to unbolt the old one, remove it, place the new one in and bolt it in place. The new one was sold as a fresh rebuild, so it should have new bearings. Since it had been sitting 20+ years in a pillow case in my dad's garage, I put some light oil on the bearings before turning the yoke by hand to verify that it took 3.5 turns of the yoke to get one turn of the ring gear. All that to say that any neglect by the prior owner shouldn't come into play here.

Now I did end up having to take the yoke off my old one and put it on the new one, and I used my electric impact on it as I've seen car youtubers do with no issues. I do think I'll check to make sure I made it to 150 ft-lb to see if the gear whine goes away (separate noise from the rumble). This whine is most audible in the 50-60 mph range regardless of throttle position. As for the rumble, on the old third member, when I replaced the seal, I also replaced the crush washer (and the old crush washer was split), and torqued that one by hand instead of with a power tool, so it wouldn't have been caused by a too loose pinion nut then (and the noise was the same with the split crush washer and the new crush washer).

One thing I was just thinking... is there a specification somewhere for the stock spring ride heights for the 1972 wagon springs vs. the 1975 wagon springs? I put new springs at all four corners when I replaced all the bushings. Mevotech doesn't seem to show that info that I can find for the SMS-803V springs. The car is a little higher up with the new springs than the old ones, but I assumed the old ones were worn, being 50 years old with 96,000 or so miles on the body. It sits level, just a little higher than before. I figured the 1975 springs might have a higher rate to deal with the extra weight of the heavier bumpers, but I thought ride height would be the same. I don't know how much higher other than "a little" because I didn't know ahead of time that I'd need to measure. I do still have the old springs, though they've been sitting outside. I'm in the desert, so not much rain. Could my best bet be to swap back to the old springs? Like where someone puts a lift kit on their truck and creates driveline angle issues? My "lift" has to be less than an inch, though.

work that’s been done with preloads and different procedures 

it’s time to pull the center section and have a true 9” specialist 

go through it and set it all up correctly! 

I mean how many times do you want to lay under the car 

“ hoping “ this or that will solve a problem?

I will go to great lengths to do 99% of my own work but sometimes you need a pro , with pro tools , and pro knowledge. 

At that point , put two new bearings on the axles , new seals , etc ..

You may be able to save most the parts in the center section , but if you drive it a bunch with out of tolerance parts you’ll end up with an 80 pound boat anchor .

Side note: anyone else with Spohn arms live in constantly windy areas? How has crosswind stability been for you? I do think mine is more sensitive to crosswinds now.

Inkara1 first mentioned the 9" was rebuilt, and he changed the pinion flange. I asked if he tightened the nut a lot installing it back, and he didn't say how he did that. So it's possible he hasn't altered the bearing crush, I also bet that he did but I don't know.

It often can take way over 200lbsft to crush the sleeve to the needed thickness, so 150lbft may not have automatically applied more bearing pressure. We're guessing, we understand how the bearing preload is set, but it's not easy to explain, or to do it.

Without knowing, my plan would be to remove the wheels and axles, and unbolt the driveshaft. Then rotate the pinion and see how it feels, how easily it rotates, and with how much play, how much resistance to rotation. If it's over tightened, the bearing preload, it might feel too "tight" that's my only idea short of removing the 9" chunk to fully look it over.

Got out the 1/4-inch beam torque wrench and measured rotational torque at the pinion as little if any above zero. So I got out the bigger 1/2-inch torque wrench and tightened the pinion nut to 160 ft-lb, then checked rotational torque again with no change. Repeated with the big torque wrench set to 170, then 175, 180, 185 and 190, at which point I had 6-8 in-lb rotational torque. I believe that's at the low end of the spec for "used bearing," so I left it there.

I could see gear oil in the driver's side axle tube (driveway isn't 100% level, it seems). Seal was doing a fine job of keeping it contained, but that tells me that I'm not low on oil.

Test drive showed little to no improvement in gear whine or 70-60 deceleration rumble. Rumble is pretty quiet or gone at other speeds, but won't go away at deceleration between 70 and 60. I did check condition of the axle bearings again, and both felt great.

*facepalm*

Inkara1 wrote: Got out the 1/4-inch beam torque wrench and measured rotational torque at the pinion as little if any above zero. So I got out the bigger 1/2-inch torque wrench and tightened the pinion nut to 160 ft-lb, then checked rotational torque again with no change. Repeated with the big torque wrench set to 170, then 175, 180, 185 and 190, at which point I had 6-8 in-lb rotational torque. I believe that's at the low end of the spec for "used bearing," so I left it there.

when you're measuring pinion bearing preload, are you turning the ring gear also or strictly just the pinion?

That stair-steppy feeling might be your noise. Or it's because you're not turning it fast enough.

A tip on replacing pinion seals(or setting up pre-load period). The only torque wrench I use is a needle one for measuring preload, I don't use a torque wrench when tightening the nut. I don't really care what torque it is, so long as it holds my pre-load. I'll tighten the nut until I get the pre-load I want. When loosening it and not replacing the crush sleeve, one has to tighten it back exactly to where it was, or a hair tighter. The only way to do that is to mark the relationship between the pinion shaft, yoke and nut with a paint stick or chisel. When doing new bearings, It can take a trial or 2 before you get it right. I'll do it originally with the seal out, get the pre-load, mark the relationship, remove the nut and yoke, and then install the seal.

I didn't know that the whole pinion gear and bearings would come out separately, it's been ages since I dealt with a 9" in any way.

That's good, but it'd be nice to know where the metal bits came from. If the bearings of the pinion were the first issue, then it might be solved by just replacing those. But who knows what else is hurt, debris can create damage to other bearings, and then the various gears. I think it'd be smart to pull the diff, and see how the rest of the gears and bearings seem. The parts are all very strong, but metal debris can hurt anything over time, the bearings would be the first to go I think. Also you need to remove as much of the bad gear oil as possible, and that means yanking the chunk to clean out the housing.

Sorry to hear of that, I've had my fill of gear work for a while. My bad 8.8 rear had tons of big gear chunks in it, and fairly decent gear oil given the carnage. My good rear that I swapped in had immaculate gear oil in it, literally clear still, no bad smell, and it had close to 95k miles on the gear oil. I had swapped a Torsen diff into it at 99k miles, with Amsoil Severe Gear, no additive(no clutches), and serviced it once at about 150k miles, still looked like new. So the gear oil I drained out at 245k this March was good enough I could have reused. I love gear only diffs, the Detroit True Trac is the next best version.

Inkara1 wrote: .... the bearings felt very grainy, and I could see chunks of flat metal in them, like what you might see in an oil pan from failing main bearings. So I ordered a new bearing set, but I'm confused as to where the pieces might have come from ....

i think what you're describing is called 'spalling'