C2 Half Shaft numbers?

[Alan Drake]

Cleaning the half shafts on a 64 and noticed each end had 3 sets of numbers, one in center and others to each side of end yoke. Unable to read center number, however the other two read "GM 90" or "GM 90 A" and the number 670775.
Very hard to read, WHAT should I find? (not F40)

Should these be polished, painted, blasted?

Thanks

[Joe L.]

Re: C2 Half Shaft numbers?

Alan------

If you're talking about a part number stamped on the tube section of the half-shaft, I've never seen such a stamping. The other numbers on the yoke ends are forging die information and/or forging part numbers. They vary.

The original tube section was natural, extruded steel tube. It's a very difficult finish to re-create. The yoke ends were natural, as-forged finish. This is very similar to natural cast iron.

[Wayne M.]

Re: C2 Half Shaft numbers?

Alan -- As Joe said, they are embossed numbers in the yoke forgings (both inboard [diff] end and outboard [trailing arm hub]).

Had a look at 2 halfshafts I have from a Feb 1964 car; 3707775 and GM90A (will mention the middle # later). other end is same except for GM90B. The other half shaft is same except that the GM90A is on both ends.

Also have 2 shot-peened halfshafts from a July 1965 big block; (same) 3707775, but with GM105A (inboard) and GM105B (outboard). The other shaft has GM120B inboard and GM120A outboard.

Seems to be no pattern as to the use of B or A. Also, I'm guessing that the GM90A is a mould number that gets updated each time the mould wears out or breaks. If this is true, the 1967 and up model year yokes will have an even higher mould # than 120.

Now for the middle numbers: on the BB halfshafts it is "1146". On the small block it looks like **7746 (unable to read first 2 digits on all 4 ends). But after looking at the BB yoke number (which is clear), I tend to believe that the middle # on the SB shafts is also 1146, and the reason I can't read what appears to be something as a prefix to 7746 is because there is nothing there; just casting roughness.

Boy, you sure are getting into every detail on your car !

[Alan Drake]

Numbers on Yoke

The numbers are all on the yoke!
The 6 is a "3" so its 3707775 and the other GM 90 is a B (I think, hard to tell)
Will check other shaft when cleaning it.
Using that RidRust stuff, does a nice job without destroying details, however it takes a long time even at 100 degrees and requires multiple refills of new fluid.
The drive shaft took a full gal, the half so far has taken the same. So its not cheap but does do a NICE job on protecting details.

Thanks for info
Alan