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Discussion Starter #1
Went to change the rear in my 70 GTO to 3:73 and found these numbers on the present ring gear: 3A42 GM LC 251
Can anyone tell me what these numbers signify? (I bought the rear some time ago as a Pontiac 3:08 12 bolt rear.) I'll count the teeth and figure out the present ratio. But I've not seen these numbers before. Hoping to be able to use the same carrier. Thanks for your help.
 

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The 12 bolt gear set is most likely a GM service (parts) gear set from much later. I've ran into similar inscribed numbers on NOS 3.31 12 bolt gear sets which I've set-up.

On your 12 bolt, am assuming the '70 is a factory 455 car, I'm keep track of original housing stamped dates & codes. If the lower right hand webbing of the center housing does not have an alphanumeric date code, would be interested in what your axle tube is stamped. Thanks!
 

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Thanks, but this is not an original 455-car. The 400 was gone when I bought it. Rear is not original either. Sorry, wish I could help you further.
Jared
 
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