Broken metal piece in bottom of differential
 

I've got the rear suspension out doing some work on the trailing arm assemblies and dropped the diff to fix a bad front pinion leak and check on side yoke wear. When I was cleaning the old fluid out, I discovered this piece of metal:

https://cimg0.ibsrv.net/gimg/www.cor...569e6fb45d.jpg

I'm guessing this is a piece from one of the clutch pack retainers? I even see the one that appears to be missing a chunk out of it:

https://cimg2.ibsrv.net/gimg/www.cor...f300139212.jpg

I'm obviously going to have to do more work than I intended on this project and at a minimum replace that retainer clip. That side of the diff has a little more side yoke play too.

I guess my questions are 1) do you agree that the metal is coming from one of the clutch retainers and 2) what would cause a failure in one of these. Are they ever under stress?

The piece doesn’t really look like it matches that hole. The space looks too round as well.

Hopefully Gary or Mike will be along shortly.

I agree. That rounded notch looks like it was machined to provide clearance for something (assembly??). Not sure what the metal piece is; but you need to determine what it is and how significant the loss is before doing any more with the 'punkin'.

What year is your differential. The 63 and 64 Dana differentials used a different clutch pack and the ears that kept it square and from rubbing the casing often break off. They look square like that and break off on the end where they were bent into a 90*. It makes it look like a radiused end,

https://cimg8.ibsrv.net/gimg/www.cor...13f24fc071.jpg
does your piece look like these
https://cimg9.ibsrv.net/gimg/www.cor...cf7672e09c.jpg
radiused bend where it broke off the case
https://cimg0.ibsrv.net/gimg/www.cor...e94a46eab6.jpg
the 2 cases on the left with the 4 legs that break off



I have a 64 rear end which they dont make parts for so I'm running it till it doesnt run anymore. Th 63 and 64 posi case is subject to cracking so GM changed venders to Eaton

. I have a 3.55 rear that can go back in and I'm going to rebuild a 69 rear end into a 3.70 to eventually replace this rear end with. Possibly next winter.The clutch pac cant go anywhere and they seem to go to the bottom of the case without doing andy damage to the teeth. Maybe just dumb luck.

It's an early 69 BB w/3.55 ratio. Looks like an Eaton posi with the earlier style square window. I will try to pull the posi out this weekend to try to get to the bottom of this. I can't get a good pic of the retainer I think is broken, but below is a pic of a retainer that is good. I circled what I think the metal piece looks like:

https://cimg9.ibsrv.net/gimg/www.cor...be2b53f38e.jpg

You should look at the part number on the case. I think the Dana case has the square opening and the Eatons have the round opening. the square angle is where it cracks.

Editted
I just looked at your first pic and compared it to the 64 pic, I think your case is definitely not a Dana case so everything I had brought up about bad cases doesn't apply

If it is that piece and you haven't had a chance yet, you should run a magnet around in there and look for the rest of it. Hopefully all the teeth look good. Good luck

Yep. Looks like a piece of that retainer. It also looks like another piece of it is still in that recess.

What you need to determine is if that retainer has any functional use after the posi is assembled. IOW, is that retainer there ONLY for initial assembly. If that is the case, you just need to capture all the pieces of that broken retainer to assure that is won't float around in the sloshing gear oil and get wedged between some gear teeth (which will instantly become broken).

I found 2 of 4 clutch pack retainers broken in my Dana 44. There was no damage to the gears. There were some scratches on the spider gear shaft likely from the pieces going through there. But nothing which was an issue.

I can't see any pictures on this pc so I don't know what you're dealing with, I will check another pc later tonight. If the part is steel, not iron, then the only steel parts inside the diff are the posi thrust washers, clutch retainers, the cross shaft and bolt. None of those should be free inside, not that I doubt it. The retainers on the Eaton posi don't get chewed up like the 80-82 Dana's, the thrust washers wouldn't come out unless the cross shaft was out and that would have locked up the diff, if a bearing cage came apart you would know it, also the snap rings will pop off if the axle is worn down and they get chewed up. All of these things are extreme, is it possible the diff was damaged, then repaired and that was left in there?

Maybe this old thread will help?

https://www.digitalcorvettes.com/for...ad.php?t=77316

The metal is steel. I'm 99% sure it is a piece of one of the retainers. I can see a chunk missing from one of them. Diff was doing fine before I dropped it this winter. I've owned the car 14 years, but it could have been worked on before. The car had an axle/half-shaft/u-joint failure at some point because the battery box and other storage compartment were both busted up pretty bad. I had to get a donor battery box to glass back in.

Unfortunately I think I'm going to be learning how to rebuild diffs very shortly because I think I see a hairline crack starting in the posi at the corner of the large window. See if you can spot it in the pic below:

https://cimg3.ibsrv.net/gimg/www.cor...a0d2326880.jpg

Can you reach it with a finger nail or small long flathead screwdriver. I had a crack appear across a accessory bolt hole on a head after I installed a motor. Turns out when I put the intake on the gasket sealant I used left a thin line across the hole that made my fingernail grab it. So I bought some new heads. As I was taking the head off I decided to really dig on it and the line came off. good news and bad. I didn't need to spend $850 on some aluminum heads but now I have aluminum heads. It looks like it could be a stray cat hair or something that blew in there. Maybe hopefully

Enlarging the picture does make it look like a crack but I cant see a line across the opening in the case. maybe a casting flaw.......

I can see the pic's now. I have found many odd things in these diff's, typically after they were previously worked on.

Here is a thrust washer I found part of .

https://img.photobucket.com/albums/v...d1groundup.jpg

Now if the diff was blown up in the past, junk may have been thrown forward into the pinion bearing well.


You can see the retainers in this picture of a posi with broken clutches.
https://img.photobucket.com/albums/v...enclutched.jpg

I can't tell if that is a crack in the posi from your picture but the brake clean test will show it. Here is one that cracked in the same area.

https://img.photobucket.com/albums/v...indowcrack.jpg

At this point you should break down the diff and completely check it, that is the only way to see what's going on. I see the spiders are 18's as well, 17's are better but that depends on your application. If you re just street driving the 18's will work. If you need a posi case the best is a NOS GM, obsoleted about 7 years ago. I bought a skid of them at the time and I am down to 3 now. A good used 72-79 posi is good, a new loaded Eaton would be my last choice.

Update on this thread:

I pulled the posi out. I was right, the broken metal was from a clutch pack retainer. Ever seen one break like this?

https://cimg4.ibsrv.net/gimg/www.cor...65220e97d5.jpg

I also confirmed that the posi does indeed have a small hairline crack starting on it. I couldn't get a good pic of it, but it does go all the way through to the inside of the posi.

The good news is that I may have a free replacement. Dad bought a wrecked 74 around 15 years ago that came with a partially disassembled differential. The side yokes and clutches are gone, but everything else is there. At first glance I don't see any cracks or issues with the new posi. It even has 17-tooth spider gears that I may be able to use.

74 posi (left) vs my early 69 (right):
https://cimg9.ibsrv.net/gimg/www.cor...626d9e65b7.jpg

Spider gears out of 74:
https://cimg0.ibsrv.net/gimg/www.cor...f6d1bbf902.jpg

So it looks like I'm going to need to put together a shopping list. I'll need a rebuild kit for the bearings/races/ring gear bolts, etc. I also want to do a tuned posi and eliminate the springs so I'll get new steel clutches and shims. Am I safe using the 17-tooth spider gears in the pic above or should I splurge for Tom's heat treated ones?

Also, what about the center pin? Mine has a little wear. Is this normal and still okay to use?
https://cimg6.ibsrv.net/gimg/www.cor...ed9aa83763.jpg

Thanks again for your help!

I'm not convinced that "hairline" crack is actually a crack. It might just be a 'witness' line from a crack in the sand mold used to cast that part. You could clean it well and use some "Spot Check" penetrant dye on it to see if it actually absorbs any dye, or not. If it isn't really cracked, it should be 'good to go' with proper cleaning and rebuild.

The tear drop case is the better of the two, crack or not. Since you have both I would use it and the 10-17's. Typically you should mark the orientation of the spiders when you remove them so they go back in the same way.

The cross shaft wear is from the axles riding into it. I replace them as part of a build since your end play will be opened the amount of wear plus the amount of the axle face dimension, and posi setup.