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I got my hands on a differential. Below is a picture of the code stamped at the bottom.
My main interest is with the back plate where the spring is bolted. I would like to use it on my 76 which has a cracked one.
However, it would seem that the 78-79 back plates are not the same as the previous years.
I could not find more details.
How do they differ? Is it something I can easily measure?
The diff reads OH 145 W9E1.
I did my home work (partly?) and found OH as being a 3:55 (confirmed with rotation).
According to my searches on the web, it can either be a 78 or 79.
Would the 9 indicate a 79 by any chance?
Not sure as to whether or not the back plate will fit your application. I'm sure someone will chime in on that. As far as the date/ production code. I'm pretty sure that it's as follows.
OH - 3.55:1 gear ratio Posi traction
145- day of the year
W- assembly plant code (Warren Motive Plant)
9 - 1979
E - May
1- first shift
Regards,
Jim
isnt there a difference in the width of the spring? Compare the spring mounting pad to your old one.
You are correct. I found the following in the Zip catalogue:
Verify spring width before ordering rear end cover: many times this has been replaced with a universal application GM part. 68-77 Corvettes used a 2-1/4" wide rear spring, 78-79 used a 2-1/2" wide spring.
Would it be correct to assume the position hole to be in the center of the mounting pad?
You are correct. I found the following in the Zip catalogue:
Verify spring width before ordering rear end cover: many times this has been replaced with a universal application GM part. 68-77 Corvettes used a 2-1/4" wide rear spring, 78-79 used a 2-1/2" wide spring.
Would it be correct to assume the position hole to be in the center of the mounting pad?
ok, let's measure what I have.
the 78-79 rear cover takes smaller bolts for mounting the spring
Excellent, it seems that I am in luck.
I just measured what I had lying around.
The back cover will take a 2.5" spring and I happen to have a composite spring around from VBP or TRW which will fit.
So I can swap the rear cover and add my new composite spring at the same time.
Diff identification help
