C3 differential
Thread Starter
3rd Gear
Joined: Feb 2017
Posts: 3
Likes: 0
C3 differential
So this is my first post I have been living on this forum for my frame off my uncle gave me his 76 before he passed that was his baby I started it last march and come along way until to I was getting ready to start my differential rebuild an I noticed that where my pinion yoke sits is off center is this ok or am I screwed and my differential cover is beat up inside where the web is can just sand it smooth and roll with it or not
Burning Brakes
Joined: Oct 2003
Posts: 836
Likes: 26
From: Harrisburg Pa
The pinion is drilled out in the center to match the ring, so an offset here is normal.
The cover rib does not hold or go against anything.
Also a stock cover it is not meant for strength, smoothing that rib is ok for stock HP but if you hammer on the car a little I would buy a cover that is meant for strength.
The cover rib does not hold or go against anything.
Also a stock cover it is not meant for strength, smoothing that rib is ok for stock HP but if you hammer on the car a little I would buy a cover that is meant for strength.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
During the 70's there was a rash of the Corvette differentials where the ring gear bolts would back out and hit the rib. Typically they would loosen one at a time and hit the rib. They would click as they did this until the rib would finally snap the bolt head off. The rear end would go quiet until the next one loosened and repeat the cycle until the ring gear would spin or metal would end up in the gears and destroy it, or the owner would investigate before it destroyed itself. Many times the only real damage was what you see to the web, of course the bolts would be damaged... 
I've never had one do it to me, but I've seen more than a few rear ends when opened that show the same evidence you have with all new bolts and lock washers on the ring gear.
Good luck... GUSTO
I've never had one do it to me, but I've seen more than a few rear ends when opened that show the same evidence you have with all new bolts and lock washers on the ring gear.
Good luck... GUSTO
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
During the 70's there was a rash of the Corvette differentials where the ring gear bolts would back out and hit the rib. Typically they would loosen one at a time and hit the rib. They would click as they did this until the rib would finally snap the bolt head off. The rear end would go quiet until the next one loosened and repeat the cycle until the ring gear would spin or metal would end up in the gears and destroy it, or the owner would investigate before it destroyed itself. Many times the only real damage was what you see to the web, of course the bolts would be damaged...
I've never had one do it to me, but I've seen more than a few rear ends when opened that show the same evidence you have with all new bolts and lock washers on the ring gear.
Good luck... GUSTO
I've never had one do it to me, but I've seen more than a few rear ends when opened that show the same evidence you have with all new bolts and lock washers on the ring gear.
Good luck... GUSTO
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
1976 is the year that had the problem with the ring gear bolts backing out. Most likely it happened here and caused the damage to the cover. Need to check the ring gear bolt holes in the carrier for damage or post some more pics. The wall in the rear cover is to prevent the ring gear from slinging oil out the vent.
Mike
Mike
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
1976 is the year that had the problem with the ring gear bolts backing out. Most likely it happened here and caused the damage to the cover. Need to check the ring gear bolt holes in the carrier for damage or post some more pics. The wall in the rear cover is to prevent the ring gear from slinging oil out the vent.
Mike
Mike
Do you know if this was common with regular 10-bolt rears, or just the Corvette IRS?In the early 90's I was redoing all of bits and pieces of the rear suspension on my '73 and learned of this issue by chance. I decided since I was at it I would pull my rear cover and check my bolts. Sure enough, my rib was missing a few bits and all of the ring gear bolts were new and all had lock washers. I had bought the car a few years earlier and it didn't occur with me so I assumed a previous owner had experienced it.
A few years later I happened to mention it to a friend that rebuilt rears as a side job and he mentioned he had a few Corvette rear covers out back so I decided to take a look. 2 or 3 out of about a dozen covers had chips out of their rib.
Good luck... GUSTO
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
It's only common on the 76 Corvettes. 78's had a few problems when they change the design of the ring gear bolts. Unusual on other years. All other GM 10 bolts used a different style locking bolt. Same 3/8-24 thread but an 11/16 serrated bolt.
Mike
Mike
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Thread Starter
3rd Gear
Joined: Feb 2017
Posts: 3
Likes: 0
Carrier
1976 is the year that had the problem with the ring gear bolts backing out. Most likely it happened here and caused the damage to the cover. Need to check the ring gear bolt holes in the carrier for damage or post some more pics. The wall in the rear cover is to prevent the ring gear from slinging oil out the vent.
Mike
Mike
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
I see three damaged bolt holes in the pic. What you can't see is the amount of runout the carrier now has. Everything could be machined and trued but it's just not worth the risk to reuse it.
Mike
Mike
Heel & Toe
Joined: Feb 2017
Posts: 17
Likes: 2
From: OH
So this is my first post I have been living on this forum for my frame off my uncle gave me his 76 before he passed that was his baby I started it last march and come along way until to I was getting ready to start my differential rebuild an I noticed that where my pinion yoke sits is off center is this ok or am I screwed and my differential cover is beat up inside where the web is can just sand it smooth and roll with it or not
Toscanoinsac - did you end up using your cover or buy a new one? I have a similar situation - not as much missing on the internal wall though. thanks
