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Username Post: Differantial Markings Question        (Topic#350633)
Valued Contributor
Posts: 2546

Loc: Northeast CT
Reg: 06-27-10
04-15-18 02:22 PM - Post#2731063    

On the side of my differential gear housing, it is stamped with two letters and 3 digits on a pad that was ground into the housing. The letters are BB, and then there is a space and 323. The casting date of the pumpkin housing is 3212 (March 21, 1962?) What do these markings designate?
Thanks Junk

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.

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Senior Member
Posts: 8488

Loc: Mustang, OK, USA
Reg: 12-25-99
04-15-18 03:24 PM - Post#2731074    
    In response to junky

These early (64-earlier) rearends have BOTH a casting date and an assembly date (which includes the gear ratio).
You have correctly interpreted the casting date-Mar 21, 62.
The BB 323 is the gear ratio code (BB=3.36, NON-posi).
The 323 is the day the rear was ASSEMBLED, Mar 23 (no year because the year is in the casting date).
So, it was cast on Mar 21 and then 2 days later it was machined and assembled with 3.36 gears, and then the BB 323 was hand stamped on the right side of the case.
This type of rear was used from 55 to 64 and 89 bazillion codes were stamped on the case through those years for 3.08 to 4.56 ratios, with both posi and non-posi rears. This same style rear was also used in 56-62 Corvettes with even different codes stamped into the case for them.
And last, WHEN INSTALLED NEW, a round disc with different cut outs was installed behind the nut at the 2 o'clock position, which was ONLY a gear ration code----------it DID NOT indicate posi or non-posi.

Attachment: rearend_ratio_discs.jpg (30.61 KB) 12 View(s)

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