12 bolt identification

Rich77 · May 17, 2020

This is in my ‘77 C10. It is a 12 bolt.
I’m trying to figure out my gears. I can’t figure out these casting digits.

Do any of you know these?

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hoagster · May 18, 2020

The F204 should be June 20 1974 and GM55 is the corporate 12 bolt axle. what I need help with is "00N2" and "3896889"

hoagster · May 18, 2020

There are pages in this forum that you can get all the information you need! my above quote is from my build page and I was able to answer my own question with all the info that has been posted in this forum. I will help you but you need to uncover some more information. All around the pumpkin you will get clues, and on the front of the axle you will get more answers.

HotRodPC · May 18, 2020

Those are just Julian date codes. Has nothing to do with gear ratio. We have plenty of info on how to figure out your gear ratio. Look in the diff section. The Squareboly library also has an index with all the stampings and where they are located on the axle tube to tell you what the factory ratio WAS and might still be.

HotRodPC · May 18, 2020

hoagster said:
There are pages in this forum that you can get all the information you need! my above quote is from my build page and I was able to answer my own question with all the info that has been posted in this forum. I will help you but you need to uncover some more information. All around the pumpkin you will get clues, and on the front of the axle you will get more answers.

You beat me to it by a hair.

Here's one link so you can calculate your ratio and KNOW what you have rather than depend on markings that might have changed.

https://www.gmsquarebody.com/threads/how-to-calculate-gear-ratio-wo-removing-covers.3860/

hoagster · May 18, 2020

It's ok @HotRodPC I have learned a lot about a truck that I have driven since I was a teenager in the 70's on this forum!!

Rich77 · May 18, 2020

Thank you!

Rich77 · May 18, 2020

Alright, I did the math. I've got 2.685 gears. That kinda blows.

12 bolt identification

Rich77

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HotRodPC

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