12 bolt rear odd shift number stamping

J's 69 · Nov 22, 2024

Our 1969 RS/SS vert has a 12 bolt posi rear, just looked at the stamping and it is BU 0521 G4 with a capital E stamped below the BU....
From the CRG decoding info I take this to be a 3.73 ratio (posi),May 21st build date , Detroit Gear and axle plant , but the number 4 in the stamping has me confused as this should designate the shift when it was built, should be a 1 or a 2 . It is clearly stamped 4 .
The E stamped below designates Eaton as the manufacturer of the 3.73 posi

Has anyone ever heard of this number 4 in shift stamping area ?

J's 69 · Nov 23, 2024

Thought it would be helpful to post a pic regarding the G 4

Kurt S · Jan 28, 2025

I've seen it once before, in a Z28 with that same axle stamp BU0521G4. Just a set-up mistake by the operator.

Shannon4570 · Jan 28, 2025

I find this kind of automotive history pretty interesting. When things were done manually who knows what could happen. Someone stamped that 4, looked at it and shrugged.

Kurt S · Jan 29, 2025

The same error still happens today. Set-up man or operator can put the date in a mold wrong, upside down, etc.

J's 69 · Jan 30, 2025

Well that sounds like it makes perfect sense to me . Funny that Kurt saw one before with the exact same axle code stamped on it . Guess they must have done several that day that had the 4 stamped on it indicating the shift that it was built on .

12 bolt rear odd shift number stamping

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