Hey, new member here. Have a question on my 72 Vette. The rear end code is E51, can anyone tell me about this code? Posi? Gear ratio?

Thx,
Kevin
72TargaBlue

Hey Kevin,

Got your email but thought I'd post here so everyone could benefit.

Appendix E of the 'Corvette Restoration Guide 1968-1982' by Richard Prince lists the following for '72 ( all positraction):
Code AA - Ratio 3.55:1
Code AB - Ratio 3.70:1
Code AC - Ratio 4.11:1
Code AX - Ratio 3.36:1
Code LR - Ratio 3.36:1

Late build '69s had a three character code but I didn't see anything like the code you have.

Thank you Jim. You know...I am confounded by that "E51" code on my rearend. And I can not seem to find a code anything like what you are talking about (i.e. AA, AB, etc.), but I will keep looking.

Kevin

Question:

Can you read the code off the rear-end without removing anything? It looks like I have to drop my leaf springs.

Thanks,
David

I don't know. To be honest with you I didn't even look for codes on the differential when I swapped out the rear spring a couple of summers ago. I should have taken more time and looked around then but I wanted to get things back together as quickly as possible and get back to driving.


Jim O.
Save the Wave...!!!

nothing in the 72 shop manual. mine has a 3.08 from the build sheet

Hi guys,

Here is what I can tell you, I'm afraid its not much help.

I have a '69 350/350 that was built September '69.

My build sheet shows 2 sets of numbers for the rear axle specification as follows:

02G81GA Positraction axle 336RA

lower on the build sheet under "comfort & con." it shows:

02GS3AA Positraction axle 336R

The black book shows RPO G81 as the positraction RPO code for all axle ratios. I'm curious to know: 1)if these codes match up with Jims restoration guide (moreso to check the accuracy of the guide)and 2)why they would have two different option no's for the same option?

Bottom line: it may take awhile to find numbers in a book that match with your C3 since there is everything from option & RPO numbers to housing casting numbers. I wonder if the NCRS would be able to help with the correct number location?

Good luck!!

ricknhis69 said: 02GS3AA Positraction axle 336R Good luck!!

I am thinking with the "AA" designation it would be a 3.55 posi rear. This is according to the shop manual. Hope it helps at least a little

"I am thinking with the "AA" designation it would be a 3.55 posi rear."

But yet on the same line on GM's build sheet it says 336.

I'm thinking that the codes changed from '69 to '72.

The build date and axle ratio codes are on the very bottom of the case, if you crawl under the back of the car you will look up at the bottom of the case where the rear case bolts up to it, on the bottom at 6 o'clock position there is the codes stamped into the case. There is just enough metal there for the stamping it may be dirty so get an old tooth brush and hit it with some cleaner I found mine wasn't sure I was looking in the right place then I cleaned it and like magic the numbers appeared!