KJLive

I have a 69 corvette that is fully customized. (It was a car of the early seventies era). I have owned the car for 25 years. I am thinking about changing out the rear for quicker performance. I found several numbers on the rear housing, but have no idea the ratio of my existing gears. I am thinking of changing to 4:11. The numbers are 1AO81269 and d119. Does anyone know how to translate these numbers? Thanks!

Gordonm

If it has been customized the rear gears might have also been changed. The only way to really tell is jack up the rear. Rotate the tire exactly one turn and count the drive shaft revolutions. If it turns 3 times a 3.08 3 1/4 turns you have a 3.36 3 1/2 a 3.55 and so on. Keep in mind if you go to a 4.11 you either need a 4 series carrier or a thick ring gear for a 3 series carrier. Do not put in a spacer, a 4 series gear on a 3 series carrier. It will break. I learned this the hard way. I am running a 3.70 gear now and it is great. The 4.11 was real tough on the highway or anything over 60 mph. I now have a Tremec with an overdrive. It is a pleasure to drive on the highway at 2200 rpm and keep up with traffic.

KJLive

Thank you very much! I appreciate it. I was thinking about buying a complete 4:11 rear from a friend and also keeping mine. Again...thanks!

Chuck Gongloff

The "8 12 69" part is the assembly date of the rear. August 12, 1969.

The D 11 9 is likely the casting date of the rear end housing. I'm guessing it's an embossed number, cast into the housing, whereas the others are stamped under the carrier.

The AO indicates a 3:70 ratio, positraction, used with small blocks. Chuck