if present it has a stamped 2-letter code indicating the ratio. I think
a 63 250hp
ordered with a 4spd would have come stock with a 3.08 non-posi., code "CZ".
If by chance it originally had a 3-spd (3,540 cars came that way, most
probably 250hp) and the 4spd was added after purchase, it would have had
the code for 3.36 non-posi, the most common ratio in '63; "CB for 3.36
"CC" for 3.55 posi, "CD" for 3.70 posi., "CE" for 4.11 posi, "CF" for
"CJ for 3.08 posi, "CX" for 3.70 non-posi.
Don't ask me why they didn't just stamp the ratio plus a "P" where
Or, place a chalk mark on the sidewall of a rear tire, at the bottom
(with the car on level pavement in neutral),
and another chalk mark on the driveshaft or a driveshaft U-joint where
you can see it if you look under the car.
Have someone slowly push the car forward for a count of 3 tire
revolutions while you scoot
along on a mechanics dolly counting how many times the driveshaft mark
makes a revolution;
divide the driveshaft revolution count by the tire revolution count and
you'll have the ratio.
The more tire revolutions you make, the more accurate this method would be.
3 tire revolutions would be 9.24 driveshaft revolutions if the ratio is
3:08, 10.1 at 3:36, 10.65 at 3:55, 12.33 at 4:11.
9 tire revolutions (multiply the above numbers by 3) would be about 27
3/4 driveshaft revolutions at 3:08 ratio, etc.
If you jacked the car up from beneath the differential and had 2 friends
rotate the rear wheels in unison
in the same direction, calling out the revolution count while you count
driveshaft revolutions as outlined above,
you'd accomplish the same thing, perhaps a bit more safely.... but you
may find that the half-shaft
U-joints have some interference when the rear wheels are hanging all the
The metal tag may have been, but none of my C-2s had one. I've always
found the code stamped into the flange where the axle cover mates to the
housing - on the bottom surface closest to the roadway.
Here's waving to ya - \||||
'67BB & '72BB
-- not affiliated with JLA forum in any way -- alt.autos.corvette is
original posting --
"To know the world intimately is the beginning of caring."
-- Ann Hayman Zwinger
You can always do what us 'old school' guys do, which is lift the
rear end off the ground, put a mark on the driveshaft, and rotate the
rear wheel 1 revolution, counting the amount of revolutions of the
Easy and simple.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.