Rear End Identification
Photos attached of the rear end in my '67. 3904351 block has been decked. Can you decipher the rear end codes?
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Re: Rear End Identification
Jim-----
I can't make out the first character of the casting date due to the angle of the photo. However, the second character is a "4" indicating the fourth day of the month indicated by whatever the first alpha character is. The last digit, "7" indicates either 1967 or 1977 (the GM #3899143 case was in production from 1967 through 1979 and, even, afterwards for SERVICE).
With regards to the case STAMPINGS, I cannot make out the first character although the second character is clearly an "A". However, for the 1967 model year the only differential code that used an "A" as the second character was "FA" (3.70:1 with HD BB axle). I can't get an "F" out of the first character no matter how I look at it. There was a 1977 axle code of "OA", though, and it's possible the first character is an "O". 1977 "OA" was a 3.08:1.In Appreciation of John Hinckley -
Re: Rear End Identification
IF the rear cover is off the same diff, the clue is the casting date C_4_7 (March 4th 1977) at the flange near the filler plug. They weren't putting cast dates on ....375 covers until calendar 1968, from what I've seen.Comment
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Re: Rear End Identification
Thank you Joe and Wayne - Based on the above I'll bet that it is an "OA" from '77. It drives like a 3.08:1......I'm gonna put it on jack stands and see. Thanks again guys - JNComment
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