Differential casting 3888140
Pro
Joined: Sep 2007
Posts: 673
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From: Calgary Alberta
The number is probably 3899143; very difficult to read after years of rust / corrosion. Used for sure 1967-up; not 1965, and not sure of 1966.
Look at the bottom at the flange between carrier and rear cover. The code will give you the assembly date. Also, under the driver side output yoke, near the bottom edge, you'll see the casting date.
