Differential Casting #s

[Larry W.]

I have been all over the web and cannot find any info on my differential.
The carrier has two numbers - C268 and 3725899. What do they mean?

Thank you for any help.

[Joe L.]

Re: Differential Casting #s

Larry-----

The casting number 3725899 was used for non-posi (i.e. "open") differential carrier housings for 1957-62 Corvettes and 1957-64 Chevrolet passenger cars. The "C268" is a date code and indicates a casting produced on March 26, 1958.

[Larry W.]

Re: Differential Casting #s

As I have a 58 it might be the original?
Thank you !

[John H.]

Re: Differential Casting #s

What's the ratio/date code stamped on the forward-facing passenger side of the housing? You may have to clean the rough-cast surface thoroughly in order to read it; the ratio code will help determine if it's original.

[Larry W.]

Re: Differential Casting #s

Those numbers don't exactly jump out at you. It appears to be - 4A402 or AA402.

[John H.]

Re: Differential Casting #s

Larry -

"402" is April 2nd, and makes sense with the March 26th casting date. However, no "AA" ratio code was ever listed as used on a C1 diff; codes for '58 were AE, AH, AN, AP, AQ, and AS, AT and AU - the last three were only used with RPO 684. If it's really "AA", it may be a passenger car diff - I don't have those ratio charts.

[Larry W.]

Re: Differential Casting #s

Thanks again. I'll check more closely and see if I can get a better read.

[Verne Frantz]

Re: Differential Casting #s

John, Larry,
AA shows up as '58 Passenger with 3.55 ratio & 3-spd trans.

Verne