Got Bad News...

[HammerDown]

Just be happy you can leave the diff in! It's a bugger to take out.
But it's still very nice to see some pictures of the project!

Greetings Peter

No pictures of this nightmare, if the pinion seal is leaking I may still drop the diff. Besides, I still need to replace the diff front rubber mount.
The bushings in my camber struts are wiped out...prior when I grabbed the wheels at 12 & 6 I got noticeable movement, could that be from the bad bushings?
The wheel bearings have no play (thankfully) but I have to find where that wheel slop was from. Trailing arms will be out in a day or so...I can only get an hour or so work time before my shoulder makes me quit.

Peter, when u had your diff out did u notice if the case was vented?

 

[HammerDown]

I must vent...the engineer that designed the trailing arm shim idea or maybe I should say, how it's a PAIN IN THE A** to get to...should be tortured!
I can't believe GM couldn't come up with a BETTER idea for the front of the trailing arms.

Yes, both of my TA bolts will need to be sawzall'ed out...I can't wait! ad

Oh, and my right side shock-mount is frozen solid, can't get the lower camber-strut off.

 

[Peer81]

Yes the case is vented. You can see it just above the diff in front of the badwing. If you need to replace the front bushing then just drop the diff and inspect it on the inside. Change the oil (lucas oil) and additive. Changes are a clip from the clutchplates came loose and is already in pieces. You can also see if your yokes and centerpen have to much wear in them. Good luck!

Greetings Peter

 

[HammerDown]

Yes the case is vented. You can see it just above the diff in front of the badwing. If you need to replace the front bushing then just drop the diff and inspect it on the inside. Change the oil (lucas oil) and additive. Changes are a clip from the clutchplates came loose and is already in pieces. You can also see if your yokes and centerpen have to much wear in them. Good luck!

Greetings Peter

What makes you say this???

Peter, on your diff did you document yoke endplay before and after the rebuild, is so what were your readings?

3 hours to get the passenger-side Trailinn-Arm out...instead of cutting through the shim-packs, I wrestled to get the RUSTED shims out then, I still had to cut the center bolt in two places...what a messed up design!

Hopefully the driverside TA is a little more forgiving.

 

[Vettehead Mikey]

What makes you say this???

Peter, on your diff did you document yoke endplay before and after the rebuild, is so what were your readings?

I'm confused too. If the clip was broken as suggested, the yoke would pull straight out of the diff.

 

[HammerDown]

I'm confused too. If the clip was broken as suggested, the yoke would pull straight out of the diff.

I don't believe Peter, is referring to the 'yoke retaining clip' but maybe one of the little 1/2 clips that hold the clutch pack in place.

I've search all over for videos etc for 80-82 diffs but can't find anything on them...all I see is from 79 and older. And I here the 80-82 diffs are different and set-up different ???

 

[Peer81]

Sorry I didn't check yoke endplay but the first time I rebuild my diff the centerpin (inside the diff) was in a really bad shape as the yokes were eating themselfs into the centerpin. The second (and last) time the vette only has about 3000miles on it so there was no sign of any wear.

Yes, Im reffering to the 1/2 moon clips that hold the clutch packs in place. Your diff cage (80-82) have a problem that on the open side of the cage a clip can come loose and fall into the oil. Then it could be pieced apart by the gears and the little metal parts can come in close contact with the bearings. I changed the cage for a redesigned cage that doesn't have this problem. But of course when you change the oil you can also look if the clutch clips are still in place.

Yes, 80-82 diffs are setup differently from the older ones. The older ones have shims to get the right preload on the side gears. Our side gears have a spring loaded shim behind them so no need to shim for the correct preload. But if your clutchpacks are still in good shape then there is no need to go this deep into your diff! After that setting backlash, preload and checking pattern is about the same as the older diffs

Greetings Peter

 

[HammerDown]

Sorry I didn't check yoke endplay but the first time I rebuild my diff the centerpin (inside the diff) was in a really bad shape as the yokes were eating themselfs into the centerpin. The second (and last) time the vette only has about 3000miles on it so there was no sign of any wear.

Yes, Im reffering to the 1/2 moon clips that hold the clutch packs in place. Your diff cage (80-82) have a problem that on the open side of the cage a clip can come loose and fall into the oil. Then it could be pieced apart by the gears and the little metal parts can come in close contact with the bearings. I changed the cage for a redesigned cage that doesn't have this problem. But of course when you change the oil you can also look if the clutch clips are still in place.

Yes, 80-82 diffs are setup differently from the older ones. The older ones have shims to get the right preload on the side gears. Our side gears have a spring loaded shim behind them so no need to shim for the correct preload. But if your clutchpacks are still in good shape then there is no need to go this deep into your diff! After that setting backlash, preload and checking pattern is about the same as the older diffs

Greetings Peter

Peter, as usual GREAT feedback but once again I must as you to clarify something above.
Are you suggesting that, through the batwing oil fill hole the clutch-clips are visible???

Well, time to cut-out the drivers side Trailing Arm...so much fun!

 

[HammerDown]

Ugh, almost three hours to cut the driver-side Trailing Arm out...to the GM designer that came up with this idea > I could hit with a bat!

 

[Peer81]

Sorry but you can't see anything by looking into the drainhole. I'm talking about removing the diff compleetly. But it's easy for me to say can't look into your ability to do this with your health limitations.

Greetings Peter

 

[HammerDown]

Drivers side Trailing Arm out and then the PITA job of getting the remaining frozen bushings out...they fought me all the way but I showed them who was boss!

 

[HammerDown]

It's out!
The front diff mount was a busted gooey mess, know wonder I could hear it 'hit' when I put the car in reverse.
I honestly thought I would see the tell-tale sign of leaking fluid from at least one of the three seals...nope.
The oily, mess all over and under the car, was either from over-greasing the u-joints (as I always do) and the oil from the 'flung' grease then separated and spread around...or...the lower diff gasket is weeping > but I don't get that 'gear oil' smell.

I'm questioning why there's more of a 'gap' on the (pictured) right yoke vs the other side???
Again, end play measured .015 on the drivers-side and .018 on the passenger side (installed)
Hoping I can borrow a pressure-washer to 'de-funk' this thing.

 

[gmjunkie]

I'm questioning why there's more of a 'gap' on the (pictured) right yoke vs the other side???
Again, end play measured .015 on the drivers-side and .018 on the passenger side (installed)
Hoping I can borrow a pressure-washer to 'de-funk' this thing.

View attachment 15672

Don't worry about it unless you have excessive end play in the yolks!(Which you don't!) No two differentials would be alike,Just would depend how it had to be shimmed to set up the ring and pinion!

 

[Vettehead Mikey]

I'm questioning why there's more of a 'gap' on the (pictured) right yoke vs the other side???
Again, end play measured .015 on the drivers-side and .018 on the passenger side (installed)

It's not a precision-assembled piece of the diff. That's part of the reason GM never specified a tolerance.

BTW- GM didn't install greasable u-joints on C3s. No need for them now either.

 

[HammerDown]

I so appreciate the feedback fellas...I'm so trying to understand 'my' 1981 diff.
The last diff I was in was my 10:10 1969 Chevelle > 12-bolt posi and that was back in 1975!

What worried me about the 'close' yoke was...I read that a wearing stub shaft/center pin will allow the yoke will grind itself into the outer diff case!

Sorry fellas, I will never install a 'non-greasable' universal where I can install one with a 'zerk' fitting > just makes sense to me. However, with the gallon of junk (like thick cake icing) I scraped from under my car, I will 'now' wipe the excess away!

Once inside I'll be curious to see what I see...but I'm not cracking it open until the outside is CLEAN!
Suppose I'll replace all three oil seals too.

More pics will follow.

 

[HammerDown]

Diff De-Funked!
Maybe I'll get it chromed > > > NOT!
Later today I'll be cracking it open like an egg...and keeping fingers crossed!

 

[Peer81]

Great to see you got it out!
Well, now the difficult part is over you can sit back and relax... ahum... :eyerole
Looking forward to the inside pics!

Greetings Peter

 

[HammerDown]

Well, it's good thing I cracked it open.

*At a quick glance, the center-pin took the worst hit, there are clear wear/flat marks (almost like a hex head nut) around the pin where at times it wasn't rotating. However, I can easily rotate the center pin with a finger.

*The stub-axles still have a 'very-slight' raised area in their centers...maybe a few thousands. Spline-marks from the stub-axles can faintly be seen on the center-pin. The stub-axles are NOT mushroomed-over as I heard would be, but just a 'slight lip' can be felt with a fingernail.

*Notice the clutch-pack retention clips...it would appear they are about to fall into the posi gears, not so, they are held where they are by the clutch pack.

*With a dial indicator on the Ring-Gear, and holding the Pinion Yoke steady, it appears I have a LOT of lash .011 thousands!

* on the end-face of the pinion gear is scribed 057 is this referenced to the shim that was used to set Pinion depth into the Ring gear???

So, what's my next move???
1) a new center-pin is for sure.
2) just go ahead and get a new clutch pack too?
3) do I purchase 'new' stub-axles or, do I chance re-manufactured stub-axles'???
Something about "reman" just has me worried but, the 'new' axles are NOT GM > both new & reman come from Loanstar Caliper.
I honestly don't want to replace 'yoke-bearings' and get into shimming the ring gear etc but, everything I know tells me, a bearing and its race (the stub-axle bearing surface) once-run are a matched pair.
*I've read where people just replace stub axles and center-pin and call it good, is this all I should be doing here?
Again, the rear made no grinding, humming or whining...over the decades when the car would sit for a few months and at rare times when coasting to a stop the clutches would 'clunk', some figure 8's in a parking lot and that was gone!

 

[Peer81]

Alright it isn't that bussy at work so here it goes!

As i see it you have minimal metal wear in the oil (and bearings) from the center pin. It is looking pretty good i would say!

If you want to change the clutch packs that is a difficult job as the side gears are spring loaded inside the case by solid metal dishes. But it can be done and as it is inside the case it isnt changing your backlash and preload.

As your ring and pinion gears don't make a sound i can say they will if your going to change bearings and shims. Advice i got from Mike and Gerry is to always change the gears when you change bearings if you still want a silent diff.

The yokes look like new to me no need to change them as there is still hardend metal on the outside (as far as i can see on my phone..)

Get a new hardend center shaft from Toms with Lucas oil and a small bottle additive.

Clutch pack is your own choice. The original yoke bearings are full roller torringtons! Most rebuild kits have 1/2 roller aftermarket bearings so leave them if they are in good shape. I would think about changing the bearing seals now you have it out, rubber gets old is only a matter of time before they begin leaking. Well that is it I think

Greetings Peter

 

[HammerDown]

Thanks for the feedback, Peter.
I do believe my stub-axles are ok to reuse.

This diff is fighting me tooth and nail.

Had to grind-off maybe .005 from a Ring-Gear tooth the get the center-pin to clear...but a bur around the center-pin from the wear marks is STOPPING it from coming out all the way. Of course there's no way to fully tap it out! ad

Then, I remove the C-clips from the yokes and a VERY slight bur around the splines won't allow those to come out of the diff! ad

Scared to use a Dremel and stone-tip to grind the burs away, I don't want the debris to get into the diff!

This car is giving me chest pains! ad