Finding Gear Ratio
Racer
Joined: May 2009
Posts: 295
Likes: 2
From: Columbus OH
On the underside of the pumpkin just in front of the rear cover there is a flat spot which has some codes. Here is a place where you can decode them:
http://www.corvettec3.ca/axle.htm
The two letter (or three in the case of a 70) tells you what ratio it came from the factory with.
http://www.corvettec3.ca/axle.htm
The two letter (or three in the case of a 70) tells you what ratio it came from the factory with.
Drifting
Joined: Jul 2008
Posts: 1,484
Likes: 459
From: Lititz PA
To be sure, you should check the ratio by counting the turns of the driveshaft. Jack up the back end of your Vette so that the rear wheels can turn. Use a couple of extra jacks to make sure it's secure. Then put a chalk mark at the 6:00 position on the inside of one of the tires. Also put a chalk mark on the bottom of the driveshaft yoke. Then count the number of turns of the driveshaft that equals exactly one turn of the tire. That's your ratio. For example; 3-1/3 turns of the driveshaft to 1-turn of the wheels will be a 3.36 gear ratio.
If you want to really get accurate, then count driveshaft turns until the wheel turns 10 times, then divide your drive shaft number of turns by 10 and you'll have your ratio.
Give it a try!
John
If you want to really get accurate, then count driveshaft turns until the wheel turns 10 times, then divide your drive shaft number of turns by 10 and you'll have your ratio.
Give it a try!
John
Thread Starter
Burning Brakes
Joined: Jul 2004
Posts: 783
Likes: 38
From: Mankato Mn
Thanks guys, I scraped the paint off & can hardly read it. It appears to be AW which would be 308 heavy duty posi. I bought the car as a project so I don't know alot about it. It came with a 396 Camaro engine & an M-21 Tranny. It has a BB hood & I'm almost sure it was originally a 427 car. I've since put a 2004R tranny in it. Do you think 308 gears will fly ?
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I just stuck a 3.08 into my 77 that has a 200-4R trans. The 3.55 was howling on the coast (that prompted the change since I had the 3.08) Works just fine IMHO.
