coltsneckbob

just got a new axle for my 442 W-30. It seems correct for the car based on the few codes I could find a resource to explain. For example:

-The axle has a SF on the passenger side tube
-It is limited slip (posi)
-Very conveniently the date code near the spreader hole is 2 months prior to the build date of the car.

Here are the codes I have no idea about:

-On the diff housing, on the front, is a code 02227 next it is CDF 2

-On the side of the housing facing front, passenger side is a code 286. The odd think about this code is it has 2 screw head shapes on either side of the number, but the number and head shapes look like part of the cast.

-In side on the large gear are the codes "13A42 GM AL 213"


Can anyone help interpret these codes? Thanks!!

rcorrigan5

I'll take a stab at a couple of your codes.

SF = on the passenger side tube indicates a 1970 anti-spin differential, 3.23:1 gear ratio. My book indicates that the 1970 W30 came with only the 3.42 rear end (code SH) or the 3.91 rear end (code SJ). However, I've heard that a person could order rear end ratios other than those two with a W30.

13A42 = on the ring gear. Divide 42 by 13 and you get your differential gear ratio of 3.23:1. A similar code might also appear on the pinion gear that results in your 3.23:1 ratio.

286 = on the side of the housing facing front is most likely the casting date of the housing, shown as a Julian date (286th day of 1969). I've heard the screw head shapes on either side of the date indicate the time of day and/or work shift.

Those are my best educated guesses! I don't know the meaning of the other codes.

Randy C.

Diego

3.23 was for W-30s with AC - not unusual.

coltsneckbob

Randy.......thanks.

Diego is correct per the resources I have found the 3.23 was standard for w-30 with air (and I have factory air).

I should have realized the 13A42 ratio was 3.23.....duh!

The 286 makes sense as the date on the housing is L16 or Dec 16th of that year.

wmachine

Welcome back Randy. Good stabs there!!!
No magic to the screw heads. They are just that: screw heads. The numbers on the differential housing (which was a casting) pretty much stayed the same for day to day production of the casting, so the numbers were more or less permanent on the casting pattern. But since the date code changed every day, it was usually a metal tag screwed onto the pattern for daily change-out. The casting definition is usually good enough to make out the tag and the screw head (until the rust gets to it enough).
You'll see "tags" like this on other castings, too, and they usually are date codes too, for the same reason. But any casting can a number added to the casting this way.
02227 Just the housing casting number, I'm reasonably sure.
next it is CDF 2 Central Foundy Division #2 (location). Central Foundry was primarily an iron foundry for all of the GM divisions (engine blocks, heads, diff housings, etc.)