delta881972

i read in a post here mention of checking the ratio by jacking the car up and turning the rear tire while counting the revolutions of the driveshaft. can anybody give me instructions on how to go about this and how to interpret my results? im assuming my 72 delta has the stock rear end (not even sure what the stock ratio is) due to the 2bbl carb on it.... seems that would be the first step in performance upgrades. a simple test like watching the driveline spin will tell me for sure.

what should the stock ratio be? its a 72 delta 350 2bbl with a th375

thanks in advance for the help

J-(Chicago)

Pull the cover and check.
The other method is only an estimate, and a waste of time in my opinion.
New fluid isn't a bad idea.

Beautiful car by the way. I used to have a 72 88 convertible.

copper128

Chances are good it'll be a 2.73 or 3.08 open.
Have you checked for the stamped code on the RH axle tube?

delta881972

thanks. i was hoping the cheaters way to check would save me some time and money lol but ya i see your point. its not a posi and no i havent checked for a code... wasnt aware there was one. can you give an example of what im looking for? ie: six digit number, letter code, 9Mxxx

thank you

svnt442

It should be a 2 letter code I believe.

OLD SKL 69

Yes, you are right, it should be a 2 letter code on the right side front of the axle tube.

Allan R

On the passenger side of the axle tube you will have stampings that identify the ratio. If you have a stock 72 Delta with a 350 it should have code NK, NA, or QJ. The first 2 are for 2:73 and 3:08. The last one is for limited slip 2:93 gears.

Here's something that might help you find the stampings

Olds64

Allan you da man!

Jamesbo

Joe P's "Cheater method"

Jack up the rear of the car. Make a chalk mark on one tire and on the driveshaft. Turn the tire ten times while counting the number of driveshaft revolutions. Divide the driveshaft revs by ten. That's the ratio. You can also do this by rotating the tire once, but the difference between 3.31 and 3.42 (as an example) is impossible to discern. On the other hand, the difference between 33.1 and 34.2 is easy to see. That's why I use ten turns of the tire.

Isn't cut and paste wonderful.

delta881972

thanks everybody! everyone here is so helpful. this is my first oldsmobile, well my first car project really, and im excited about doing a lot of it myself. i dont know what i would do without having a resource like your olds forum to glean information, ideas, and instructions from!

thanks again to everyone here that helps out those of us who would be lost otherwise

Olds64

I bet you have a 4.88 spool in your car!