The differential numbers are 3969278. The numbers on the right axle tube are XT K257E. Thanks.

cast# for a 12-bolt (should be 70-72 axle)
code xt = ???
date K257E = ??? + posi-traction (E)

here's what was found on the http://www.chevellestuff.com/qd/generic_rear_axle_info.htm
about this axle


Example: CHC0642E decodes to CHC ~ 2.73 Positraction, 064 ~ day of year starting with January 1 (the 64th day being March 5), Chevrolet, 1 or 2 ~ shift (if present), - ~ no Positraction, p ~ Positraction, E ~ Eaton Positraction
B = Buick, O = Olds, C or G = Chevrolet, K or M = McKinnon Industries, or P = Pontiac.

Casting Numbers:
12-Bolt Casting #3969278

Recently I've been asked a couple of questions about, what appears to be, McKinnon Industries-built (GM of Canada) rear ends that seem to have odd - or non listed - ratio ID codes.

One is casting number 3969278 (1970-1972), dated F209, and coded XT 0911 K. Another is casting number 3959038 (1969), no casting date as of yet, and coded LE 11 15 K.

I cannot find information in either my U.S. or Canada parts & accessory catalogs. Any help in identifying axle ratios for these two prefixes or any other McKinnon Industries rear ends with other prefixes not listed on this site would be welcomed.

best i found. :)

Thanks Vince. Good information.:thumbsup:

i believe that is a pontiac code. they used chevy 12 bolts in other than chevy's. 69 olds that went to canada and pontiac used them for the big engined A body's. tom

Hollander shows an XT listed for 69-72 Pontiac A body (3.07posi) if that helps.

I actually got the rear from a 70 Monte Carlo many years ago. I'm not sure if it was factory to the MC or not.

'70 Monte Carlo only had 4 ratios available but used the same codes as the Chevelle's for those 4.
FWIW :The '70 Chevelle's had a total of 8 ratios.
Closest Chevelle/MC code's to yours are the 73's which were XB ,XC & XE.

got a 12bolt gave to me need to know what i got 3896839 N

Welcome to TC Steve.
You really need to start your own thread as your on one that's been stale since Jan 09.
Look's like a truck 12 bolt -coil or leaf spring ?
Get more info
http://img.photobucket.com/albums/v466/Pontiac1976/axlecodeDiff.gif