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Discussion Starter #1 (Edited)
Hi everybody. I bought a 78 Power Wagon from a friend who bought it from a guy in Los Alamos. 53,000 on the clock but the speedo doesn't work so that's questionable. So, my friend was driving it back to his place when the rear end starting making a lot of noise and the truck became nearly impossible to drive. That's all he really knew about the truck. He didn't have time to fix it and I do so, lucky me. Here it is:
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I trailered it to my place and was able to drive it into the shop. There is a rhythmic grinding sound from the rear diff. The driver's side rear wheel did drag and skip in both HI and HI LOC. Engine sounds amazing, by the way, even though it has about 1/2" of oily crud protecting its finish. I pulled the diff plug out and, I'm no SAE mechanic but, isn't there supposed to be fluid in the diff?
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'Cuz there wasn't any. At all. Finger dry as a bone when I reached in. I guess the diff fluid was busy holding all of the mud on the pumpkin cover?

I opened up the diff and am not sure what I'm looking at. There are definitely metal shavings but is that brown crud sawdust?
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It's not rust and it's not hard. I can squeeze oil out of it.

That mud at the bottom is the only fluid in the diff.
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Here's what I can see of the pinion:
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I'm going to finish disassembling the diff. Something is toast in there.

Mainly though, I'm curious if y'all think that brown stuff is actually sawdust. If not, what is it?
 

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You need new gears, That pinion is shot. Take eveything apart and see what else is history. Did you happen to look at the front one?
 

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Discussion Starter #3
You need new gears, That pinion is shot. Take eveything apart and see what else is history. Did you happen to look at the front one?
Yep, the pinion is shot. I have the diff out now and there are chunks missing out of the ends of several of the teeth.

I'll check the front end tomorrow. Wouldn't be surprised if it was in similar shape.
 

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Discussion Starter #4
There was a fair amount of play in the pinion, both laterally and longitudinally. I've already ordered a replacement ring and pinion. I started to remove the preload springs from the carrier and judging by how difficult they are to get out, I am wondering if this type of differential was meant to be rebuilt. I can't see any way to inspect the spider gears without removing the preload spring pack.
 

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Discussion Starter #5
The pinion is stuck. I'm taking the axle housing off later today to get better access to the pinion as there is nothing left to do with it in the truck other than continue to fruitlessly hit it. Plus, if I cannot get it out, I already have the axle out for a replacement. Which leads to my question...

I've read through the forums and had most of my questions about a potential rear end swap answered and only have these questions remaining: What rear ends will bolt directly on as replacements and, failing that, can I use basically any 9.25 3.55 rear end if I can potentially move spring perches? Local junque yards are dirty with 1500s and Durangos with 9.25s geared for 3.55. Do they have the same lug pattern as my W150?
 

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Discussion Starter #7
Thanks a lot, Moparite. I ended up buying a '76 rear end with a 90 day warranty from a junk yard. I'll switch them out today, do a brake bleed and maybe finally get to drive my truck!
 

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Discussion Starter #8
The junk yard rear end I bought ended up having a badly deformed outer pinion bearing and seal that immediately leaked when I filled the diff. I removed the axle assembly and am positive that was well worth the extra half hour of work. Disassembly was straightforward and I quickly found that there was no pre-load on the outer pinion bearing. In fact, the crush sleeve hadn't been crushed at all and the bearing was loose in the cup.
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Rebuild of the differential itself was straightforward. I don't see how this job can be completed without a press. Setup bearings are a necessity unless you happen to be the luckiest person ever. If you make setup bearings, adjusting everything isn't quite as difficult or annoying as a lot of people seem to think. After you've done it a few times, you can go from a properly pre-loaded pinion set at the incorrect depth to changing the shims on the inner pinion in 20 minutes. Randy's and Yukon ended up being excellent resources. If you do remove the rear end, you will probably want to get new U bolts as you'll probably need to cut them to get the axle assembly off of the leaf springs.

The rebuilt rear end is totally quiet. The famous Dodge clunk is there but there is no sound from the rear end and the area around the outer pinion bearing is barely warm to the touch after driving. Unfortunately, I did notice oil leaking from under the timing cover so looks I'll be into that next.
 
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