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Discussion Starter #1
Been shoppin on Toms page. Am I reading this thing right? I see polished case $240, Internals kit $240 and $115 labor, so $600 for a tuned differential. Gary, Opinion on what I would get for that and what else would I need to do to the rest of the rearend on my 81? Would I need a 3 series or 4? Yoke bearings, shims and seals? Bearing cap improvements?
Target is a somewhat bullet proof rearend incase I get stupid at county line or morosso.
My motor should be in the neighborhood of 350hp, maybe a little more, street tires and a 2004R, built by me.
 

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6', me hardly in Gary's class on diffy's....notice I didn't say rears...:rolling:

but I redid my diffy myself using decent GM parts from a stealership some 12 years ago....had to swap the case due to leaking some 8 years ago down here....not an issue....thing is fine....so far...

but YMMV, for sure....I DO wish I had all his posting to go by back when, but so far so good....I put the swirl marks in the center of the ring gear, instead of to the inside, not knowing....oh well...

Course, my engine is mild, and it's only 336 with 10" street rubber Nitto's and its a RARE burnout....damn tires ain't cheeeeep anymore

:cheers:
 

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Discussion Starter #3
The general concensus seems to be that the diff on late C3's is crap, okfine. So, if I want a mediaup to high hp stable diff, what to do? The Batwing seems to be a pretty good design, so the weaklink is the u-joints, yokes and internals for the diff. So thats what I am trying to figger out, which way to go to make it stronger..
The one I have is ok, not worn or real out of spec. But eventually I'll have this thing back on the road and would have to break something back there first time I stick my foot in it.
 

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The 80 -82 diff's are not the ones I work on. I would say some things about them but I don't want to offend anyone.

Mike Tracdogg rebuilds them and that's who I refer them to.

There's not too much I can do with them other then a stock rebuild and I would have get some setup bearings to do them.

I would bolt up an iron unit if I owned one of these, but that would cost more.
Some guys have 400-500 HP in front of them and have no problems but I've seen too many that came apart with the stock drivetrain.

The 63-79's I can build just short of a 12 bolt. I have been tempted to do a 12 bolt but I don't have a 12 bolt case around and the cost is too high for most guys other then pure drag racers. A solid built 10 bolt will handle most street applications.

Keeping that in mind, you've probably seen the pictures of "iron salad" the posi my son destroyed in his 75 with 370 HP. Continues abuse finally cracked the posi in 1/2 at 8k miles, not before 200' burnouts and burning the rear tires bald in 8 k miles. That case was weak to begin with since it was hit by the pinion earlier in it's life. It would have lasted under "normal" street operation:smack
 

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Discussion Starter #5
Thanks Gary
 

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Six,
The problem with the 80-82 diffs is the caps carry the side loading from the carrier. The 63=79 use the case to support it. The caps have a raised lip that the bearing race pushes against. This design was changed in '84. The strongest carrier with the best gears won't make the diff any stronger. The best solution is to convert to the older iron set-up.
Mike
 

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Discussion Starter #7
Hey Mike
I didn't even realize you posted in here, I was going to post this in CF.
Would a 6 link releive that? I am having a hard time visualizing what your talking about since I don't have a book here
 

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I was invited to come over here so I don't post must over there anymore. I don't have any pics of the 80-82 diff to show you what I'm referring to. It's a design problem that there isn't a fix for. Marck did the next best thing by adapting a C4 D44 into his. The six-link won't help any since this is an internal problem.
Mike
 

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I was invited to come over here so I don't post must over there anymore. I don't have any pics of the 80-82 diff to show you what I'm referring to. It's a design problem that there isn't a fix for. Marck did the next best thing by adapting a C4 D44 into his. The six-link won't help any since this is an internal problem.
Mike
Mike, what specifically is the problem?? don't need pix...a good description is fine by me....

I been thinking and now looking at a C4 diffy/suspension conversion....

but I dunno about MONEY time/effort....

:crazy: :cheers:
 

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Here are pics of an 82 case. Mike, what raised lip do you mean? Must be the raised step behind the bearing race, you can see it in the pics below. The caps themselves rest against the case on the sides. Another big issue IMO is that first the caps are cast and second the mating face of the cap and the case is as cast also, making for a very poor preload. Sure, you spread the case but it's very common to find a wear pattern on the bearing race that is all over the place, not a ncie smooth circle but more like a sine graph if you get what I mean. The later C4 differentials have forged caps and machined mating surfaces. The sideways support however is still the same

82 Dana 44 (same as 80 & 81) carrier:







C4 super Dana 44

 

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Here are some more pics of the brilliant raised lip system, you can see how it supports the side bearings here.


 

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Six,
The problem with the 80-82 diffs is the caps carry the side loading from the carrier. The 63=79 use the case to support it. The caps have a raised lip that the bearing race pushes against. This design was changed in '84. The strongest carrier with the best gears won't make the diff any stronger. The best solution is to convert to the older iron set-up.
Mike
I guess i don't understand. The side yokes have c-clips that support pulling loads and the end of the side yoke rests against the center spider gear pin. So the side loading is supported by the carrier. NO?

The soft ended side yokes are always wearing out against the pin. The pin wears a flat spot in it as well.
 

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Thanks Marck, you did a better job explaining it than I was doing. You can see in the pics the difference between the cases and caps.
Mike
 

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Discussion Starter #14
OK, I think I am starting to understand. So the issue is how the carrier is mounted in the case with the bearing caps? Is the diff case itself the problem, not strong enough?
 

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Here are pics of an 82 case. Mike, what raised lip do you mean? Must be the raised step behind the bearing race, you can see it in the pics below. The caps themselves rest against the case on the sides. Another big issue IMO is that first the caps are cast and second the mating face of the cap and the case is as cast also, making for a very poor preload. ]
wait a minute. What does how tight the cap squeezes the race have to do with preload? Nothin.

You don't want to distort the race, but the preload is determined by how many shims you put in.

It don't look good, but its a non issue.

point 2. What does it matter if the cap touches the case. There is no side loading there.

i still don't understand the lip thing. Like i said in the other post, side loading is supported by the center pin in the carrier. The yoke bearings are needle bearings not thrust so i don't see how the case takes any load other than at the carrier bearing.
 

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I guess i don't understand. The side yokes have c-clips that support pulling loads and the end of the side yoke rests against the center spider gear pin. So the side loading is supported by the carrier. NO?

The soft ended side yokes are always wearing out against the pin. The pin wears a flat spot in it as well.

AND your question to ME anyway, put the entire discussion clear to me...

when the carrier is pushed side/side by the output yokes....it's got only the outer bearing race to stop it from sliding side/side....and if the case is not there, and only the caps are....it's a totallized failure guaranteed....

which is what TT/others are talking about with going 4 links on the top/bottom and floating the output shafts...releasing the c-clips...and grinding down the ends of the output yokes for clearance....

NOW, I just undersand summfin more.....

:D :devil:
 

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wait a minute. What does how tight the cap squeezes the race have to do with preload? Nothin.

You don't want to distort the race, but the preload is determined by how many shims you put in.

It don't look good, but its a non issue.

point 2. What does it matter if the cap touches the case. There is no side loading there.

i still don't understand the lip thing. Like i said in the other post, side loading is supported by the center pin in the carrier. The yoke bearings are needle bearings not thrust so i don't see how the case takes any load other than at the carrier bearing.

The cap has to hold the race, hence the .001 preload. Too loose the race will twist or spin.
Preload is adjusted by shims. To have preload the bearing/race is being forced against the case and cap.
There is extreme side loading. Every time you hit the gas the pinion tries to push the ring gear away.
The stub axle pushes on the pin. The pin pushes on the carrier. The carrier pushes on the case and cap.
On the iron cases the case carries 100% of the preload and sideloading. On the Dana the case carries half the load, the cap carries the other half. Compare the last two pics Marck posted.
Mike
 

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Discussion Starter #19
OK< I think I am seeint it now too:
In The iron units the shims provide the preload and are between the case and outboard side of the bearing so the case carries the load.
On the Dana, it looks like the shims are between the bearin and the carrier?
yess/no?
 

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wait a minute. What does how tight the cap squeezes the race have to do with preload? Nothin.

You don't want to distort the race, but the preload is determined by how many shims you put in.

It don't look good, but its a non issue.

point 2. What does it matter if the cap touches the case. There is no side loading there.

i still don't understand the lip thing. Like i said in the other post, side loading is supported by the center pin in the carrier. The yoke bearings are needle bearings not thrust so i don't see how the case takes any load other than at the carrier bearing.
It's not about how the cap squeezes, it's about that the cap takes half of the side loading AND on top of this, the caps are sitting on a non machined surface and are only pressing against the side of the case, which is also as cast. This means there is nothing to positivly place the cap and ensure that the bore is perfect and the cap sitting perfectly straight. It's a real cheap solution. If you ever take apart one of thse and inspect the wear marks on the bearing race you will see how it walks about. The preload is indeed set with the bearings, but the thrust surface is comprised of both cap and case.

Here's an iron case, you can see where the whole case takes the load. On these the shim pack (or in stock shape 1 big cast iron machined shim) goes, between the race and the case. On the danas they go between the bearing and the carrier.

 
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