Rear End Ratios

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god.favored

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I hope this is in the right spot
im looking to change out the rear end gears in my 64 valiant, theres no tag or anything on the rear end so i put it up on jack stands and turned the driveline and it ended up being 2 rotations of the driveline was 1 turn of the wheel. so im guessing that means its like a 4:1 ???

if so ive found an old service manuel and the standard gear ration was 3.23, 3.55, or 2.76 and i was wondering what to expect from each of these. its the 3 speed push auto (2 barrel 276) and right now it wont go past 60 so i cant use it on the highway much. i would like it to be pretty good for daily driving but have some acceleration too any info would be great thanks guys
 
To properly check it you have to make sure both drive wheels turn the exact amount. 1 turn in this case. If both wheels turn exactly 1 turn and the driveshaft turns 3-1/4 times it's a 3:23 ratio. If the driveshaft turns a little less than 3 turns it's a 2:94 ratio, etc.
 
fishy68 said:
Read my first reply again and do it that way. It's the same whether you have a sure-grip (a posi is a Chevy term. Both are the same operating characteristics) or an open.
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sorry im still really new to this (haha im only 17) and when i get it up on the jackstands only one wheel spins while i turn the driveshaft. so im not sure how im supposed to make sure both wheels turn if only 1 will.... (sry i know this is prolly a stupid question but i really dont know)
 
Once the car is jacked up, make a mark on both tires at 12 o`clock and another on the side of the driveshaft. Now rotate the wheel while you watch the driveshaft. Count the revolutions the driveshaft rotates for one rotation of the wheels. That will be the approximate gear ratio.
 
Longgone said:
Once the car is jacked up, make a mark on both tires at 12 o`clock and another on the side of the driveshaft. Now rotate the wheel while you watch the driveshaft. Count the revolutions the driveshaft rotates for one rotation of the wheels. That will be the approximate gear ratio.
Click to expand...

Assuming it is a posi, those procedures are correct.

If it is an open, only jack one side and leave the other tire on the ground. Rotate the tire, on the jacked side, one full revolution, counting the revolutions and partial revolutions of the driveshaft, double that amount, and that is your gear ratio.

So, for example if you counted 1 3/4 turns, you have a 3.55.
 
god.favored said:
sorry im still really new to this (haha im only 17) and when i get it up on the jackstands only one wheel spins while i turn the driveshaft. so im not sure how im supposed to make sure both wheels turn if only 1 will.... (sry i know this is prolly a stupid question but i really dont know)
Click to expand...

No problem. In a case like that it takes 2 people to make sure both turn a full turn. And it's not a stupid question. We all have to learn.

I see there are 3 responses to the question now (counting mine) and as I look at them close they accomplish the same thing. Just put in different terminology.
 
god.favored said:
sorry im still really new to this (haha im only 17) and when i get it up on the jackstands only one wheel spins while i turn the driveshaft. so im not sure how im supposed to make sure both wheels turn if only 1 will.... (sry i know this is prolly a stupid question but i really dont know)
Click to expand...

There are no stupid questions, everybody has to start somewhere.
 
Brad4406 said:
Assuming it is a posi, those procedures are correct.

If it is an open, only jack one side and leave the other tire on the ground. Rotate the tire, on the jacked side, one full revolution, counting the revolutions and partial revolutions of the driveshaft, double that amount, and that is your gear ratio.

So, for example if you counted 1 3/4 turns, you have a 3.55.
Click to expand...

Hey thanks I did it that way and ended up with about a 4.10 is what I'm thinking so I'll prolly get some 3.23's for it
 
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