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Differential Decoding

Old Jul 5, 2024 | 08:06 PM
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Default Differential Decoding

I'm helping a family friend clean out a garage full of old 63-67 Corvette parts.... significant other has been placed in assisted living facility.

Looking to decode the following differential .....handwrittten tag on it reads 3:70....trying to confirm.

Part numbers found:
3871375 - differential cover
Date reads: 9 68

3899148
Code reads: 2C AG (or AC...difficult to read-- weak stamp) 5-18-70

Appreciate any insights...thanks.
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Old Jul 5, 2024 | 09:15 PM
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Default Axle codes

I uploaded a shot of the axle codes from the NCRS judging manual, 6th edition. If the letter you are struggling to read is an "O", then that would indicate a 3.70 positraction axle. The leading "2" indicates 2nd shift production.


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Old Jul 5, 2024 | 10:30 PM
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The best way to confirm the gear ratio is to mark the input, turn the "wheel" and count the rotations. Just make sure that the positraction is working, and both sides turn together.
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Old Jul 5, 2024 | 11:24 PM
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CAO is a 3:70 ratio for a car delivered with a 350 engine.
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Old Jul 7, 2024 | 01:35 PM
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Appreciate the input from all. I received another picture from the owner after further cleaning the casing.....

The number is 2CAO51870W.

If I'm reading/ understanding the coding correctly, this interprets to 2nd shift/ 3:70 Posi/ May 18, 1970/ Warner Gear.....is this correct?

Thank you.
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Old Jul 7, 2024 | 05:11 PM
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We’ve got a winner!
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Old May 20, 2025 | 06:34 AM
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…. And now…. Back to the question at hand, please…. Where do I find a late 1969 differential for my car? Could I use the internals of my existing differential in another case?
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Old May 20, 2025 | 07:44 AM
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Originally Posted by Apollo 13
…. And now…. Back to the question at hand, please…. Where do I find a late 1969 differential for my car? Could I use the internals of my existing differential in another case?
I have found several differentials via Craigslist. Facebook Marketplace is another potential. Putting a WTB on the Parts subforum is another.

Yes, you can transfer all your internals to the 69 case except the caps as they are matched (left/right) to the case (bores machined).
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