Well my C6 is being rebuilt. I’ve got an oval tag with a set of info numbers and I have a long number stamped into the housing. Trying to figure out what the numbers mean. Tranny man told me it is a
66 transmission for mustang/cougar. Man this thing was fried…this will be the first rebuild for the tranny according to him.
In 1967 it was federal law that all 4 speed manual transmissions be stamped with the car’s VIN number. Unfortunately this was not applicable to any other kind of transmission. There’s not any way to say if that transmission came with that car. Or that it didn’t.
Like Royce said, you can’t difinitively say yes or no. But you can look at the various casting dates on the transmission and compare them with the build date of your car. Also be sure to verify that your car actually came with that model of transmission (which I imagine you’ve done already?).
If any of the dates are after your build date then there is no way it came in your car originally. Typically they say casting dates should be 4-6 weeks prior to the cars build date, but this can vary a bit depending on the production period.
I don’t think there are any casting dates on a C6. At least none that I have been able to identify as such. There are casting ID numbers like the C6AP XXX-XX on the case of 1966 - 67 C6 transmissions.
Not sure why. I didn’t find any on the '68 C6 either, but maybe I don’t know what to look for. The '68 C6 used a C8AP - XXX- X case casting. Here are some photos of an NOS 1968 C6, it may be that paint marks were the only way to ID.