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12 bolt codes / casting numbers and rear axle ? help

61K views 16 replies 6 participants last post by  Jm1966 
#1 ·
Hello guys, i crawled under the car , cleaned the housing found some codes , i need some help please to de-code-i did a search on the web but i can come up with nothing certain... so here are the numbers ;

looking from the back at the 12 bolt housing
(driver side) top left 12 on top and 67880 just below
(passenger side) bottom right corner 55 L 4 8 or B :confused:

the only thing I decoded is L 4 8 - could be december 4 th 1968 , correct ? 55 ?

i ve been tryng to find the rear axle codes in order to find out the gear ratio but this code should be on the other side of the rear shaft , so i guess i need to raise the car somehow to find those numbers

thanks for any help... :thumbsup:
 
#3 ·
Hi , yes... This is where i was looking and i decoded - L 4 8

but the other numbers i have are not there or maybe i m not finding them .... nor the axle codes :confused:
 
#5 ·
Mike thanks , so those numbers are just foundry numbers... so in the following link there is the " codes location " but i scraped and cleaned i found nothing... could it be its on the other side ?

http://www.chevelles.com/years/69/69rearcodes.html
 
#6 ·
Look on the front of the passenger side axle tube for the code about half way between the center section and the brake backing plate..
Didn't realize Dale was showing it on the back of the tube ,close to the center section.
I wouldn't trust the code to be what's inside a 43 year old rear ,I'd pull the cover and get the gear info.
The rear could probably use a lube change after 43 years ;)
 
#7 ·
Hi Oliver,
With a Foundry Date of December 4, 1968, your Casting Number should be 3917124.
 
#8 ·
I guess i have to take the car to the garage i think its impossible to crawl under to look at the front side of the shafts ... but anyway thanks for the help .. and let you know if i find anything... ciao
 
#13 ·
Dale, sorry i m getting confused - where are the codes on back or on front side of the tube ? - passenger - left side- looking at the car from the back
I scrubbed really hard on the back but have not found any ...
Thank you for the help
 
#14 ·
{edit - added photo}

The STAMPED codes are suppose to be on the passenger side front of the axle housing. These are not gang stamped and they're often not real deep either. GM parts book says they should be 8"-10" inboard of the backing plate but GM (itself) often didn't stamp them so there's no real measurement to go by. As you can see from teh photo I have of the 67 on that page, the stamping is more towards the center section but that's just from that person, that day, at that plant.

Again, road grime and paint from someone wishing to spruce up the looks underneath can make it hard to find.

 
#15 ·
Great Dale, all is clear now..I ll try to find them ...have nothing better to do in rainy sundays anyway... Thanks again ciao
 
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