C3 diff issues?
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Jul 3, 2022, 10:04 PM
Tech Contributor
Joined: Aug 1999
Posts: 15,173
Likes: 3,982
From: Connecticut, USA
Sure I'll play.
1976 original corvette differential issues
1976 original corvette differential issues
- Abuse- broken parts inside
- posi case cracked
- ring gear bolt backed out, gouging the posi web side and the LH wall.
- axles worn down, crashing into the lip over the seal, grinding it down into the seal, causing large oil leak and possibly wrecking the housing. If standard axles were installed the back side of the ubolts cut into the housing ears
- pinion seal leak- not sealing the splines, ripping the new seal, using a cheapo seal to save $5
- broken snowflake clutches in a manual car with 370-411 gears
- Elongated posi cross shaft holes causing excessive axle endplay
- broken cross shaft bolt, possibly blown out the side of the posi case
- pinion crashing into the posi case after someone rebuilt the diff or just replaced the pinion seal and didn't know about checking it for clearance.
- wrong size bolts used in the strut rod bracket or cover plate for the spring, cracking the housing causing an oil leak
- Probably the best one that could include most of the above- inexperienced and production shop service.
Tech Contributor
Joined: Aug 1999
Posts: 15,173
Likes: 3,982
From: Connecticut, USA
Sure I'll play.
1976 original corvette differential issues
1976 original corvette differential issues
- Abuse- broken parts inside
- posi case cracked
- ring gear bolt backed out, gouging the posi web side and the LH wall.
- axles worn down, crashing into the lip over the seal, grinding it down into the seal, causing large oil leak and possibly wrecking the housing. If standard axles were installed the back side of the ubolts cut into the housing ears
- pinion seal leak- not sealing the splines, ripping the new seal, using a cheapo seal to save $5
- broken snowflake clutches in a manual car with 370-411 gears
- Elongated posi cross shaft holes causing excessive axle endplay
- broken cross shaft bolt, possibly blown out the side of the posi case
- pinion crashing into the posi case after someone rebuilt the diff or just replaced the pinion seal and didn't know about checking it for clearance.
- wrong size bolts used in the strut rod bracket or cover plate for the spring, cracking the housing causing an oil leak
- Probably the best one that could include most of the above- inexperienced and production shop service.
Thread Starter
Heel & Toe
Joined: Sep 2010
Posts: 16
Likes: 8
So far.......my only diff issue appears to be rear wheel movement when I had it up on the rack for a front end alignment.
The mechanic was able to move the right rear wheel in/out 1 inch(or more) and a small amount on the left. Not the wheel bearings. as it slides in/out on the drive shaft.
No noise and no fluid below the diff.
Perhaps the axle shaft worn....that goes from the yoke into the diff?
The mechanic was able to move the right rear wheel in/out 1 inch(or more) and a small amount on the left. Not the wheel bearings. as it slides in/out on the drive shaft.
No noise and no fluid below the diff.
Perhaps the axle shaft worn....that goes from the yoke into the diff?
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,209
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Ve broken teeth ona 3.70 older diff, have another 3.55 that is going, but the current 4.11runs strong
Thread Starter
Heel & Toe
Joined: Sep 2010
Posts: 16
Likes: 8
Guess I am going to need these, at the very least.....C3 Corvette 1968-1979 Differential Side Yoke | Corvette Mods
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Le Mans Master
Joined: Jun 2019
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From: Indiana
Guess I am going to need these, at the very least.....C3 Corvette 1968-1979 Differential Side Yoke | Corvette Mods
https://www.corvetteforum.com/forums...ay-advice.html
the chore will be to find the correct hardened axles..
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,082
Likes: 4,431
From: Marlton NJ
Just so you know... @GTR1999 is probably the singular top authority on these diffs in the whole USA, now that Tom of Toms Diffs has passed. He has rebuilt 100s and is a regular contributor on this forum.
He says GMs heat treating changed around 70-72 or so, and the ones after that wore very quickly. I had a pair that (76) that wore about 1/2" off the diff end. The vast majority of the rebuilt or aftermarket axle yokes available are of very cheap quality as well. Do LOTS of research before buying. Especially do an "advanced search" here for Gary's @GTR1999 comments on the subject of yokes.
Your best option may be to find a pair of original yokes of any year that do not look like they have too much wear, and send them out and have the ends "hardened".
Obviously inspect and measure yours before you do anything.
OTOH if you are not really going to put many miles on the car, it just becomes another "wear item"
Oh and Corvette Mods is not very well regarded on this forum. Van Steel and Bairs are 2 of the best.
Best of luck in your quest!
He says GMs heat treating changed around 70-72 or so, and the ones after that wore very quickly. I had a pair that (76) that wore about 1/2" off the diff end. The vast majority of the rebuilt or aftermarket axle yokes available are of very cheap quality as well. Do LOTS of research before buying. Especially do an "advanced search" here for Gary's @GTR1999 comments on the subject of yokes.
Your best option may be to find a pair of original yokes of any year that do not look like they have too much wear, and send them out and have the ends "hardened".
Obviously inspect and measure yours before you do anything.
OTOH if you are not really going to put many miles on the car, it just becomes another "wear item"
Oh and Corvette Mods is not very well regarded on this forum. Van Steel and Bairs are 2 of the best.
Best of luck in your quest!
Tech Contributor
Joined: Aug 1999
Posts: 15,173
Likes: 3,982
From: Connecticut, USA
I am addressing axle questions on the C3 Facebook page now, with pictures. If I posted them here some may have an issue.
You have worn axles and probably other potential issues going on inside. 76 was in the range group of problems I listed above. Read and understand it or you will end up paying more for less.
One thing if you think all parts are the same forget it. The quality today varies a lot.
You have worn axles and probably other potential issues going on inside. 76 was in the range group of problems I listed above. Read and understand it or you will end up paying more for less.
One thing if you think all parts are the same forget it. The quality today varies a lot.