Gear ratio calculator
Thread Starter
Racer
Joined: Feb 2009
Posts: 343
Likes: 0
From: San Diego CA
Gear ratio calculator
How to use one with a slippery torque covertor? I've always figured my '76 to have a 3:08 rear end but now I'm wondering. It was a virginal 50K mile L-48 car when I started restomodding it. So I'm sure the original owner never put a 4:xx rear end in it. Yet that's what the couple of gear ratio calculators I've tried are showing. I used to use SmokeEmUp's website but now it's fee based. So I just googled a couple and ran the numbers.
I figure the reason I'm getting bad info is because of my 2500 stall convertor.
Using 27" tall tires (255/60r15) and a Turbo 350, it runs 3400RPM at 65MPH. By then the convertor has certainly gone into full engagement, so I don't know why the gear ratio calculators show gears so low.
I figure the reason I'm getting bad info is because of my 2500 stall convertor.
Using 27" tall tires (255/60r15) and a Turbo 350, it runs 3400RPM at 65MPH. By then the convertor has certainly gone into full engagement, so I don't know why the gear ratio calculators show gears so low.
Burning Brakes
Joined: Nov 2006
Posts: 954
Likes: 40
2022 C3 of the Year Finalist - Modified
If you want to know what is the rear end ratio put the back two wheel on air and count how many turns make the driveshaft for one turn of the wheel this will be your ratio in the rear end, by that you eliminate other errors or faults.
Avner
Avner
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
With a loose converter there is to much room for error using a gear ratio calculater. Your tach could be slightly off also. This is a sure fire method.
Thread Starter
Racer
Joined: Feb 2009
Posts: 343
Likes: 0
From: San Diego CA
RE: spinning the driveshaft-sure that's an easy way but I don't think it's precise. Certainly though, one could tell a 3:xx gear from a 4:xx gear. That's for sure. You wouldn't be able to tell a 3:23 from a 3:08 though.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
It would be slightly more difficult if you were blind, but even then you could tell by your tactile senses. If you know the available ratios, you will have enough information to deduce the result. You'd have a convincing agruement if the distinction was say a 3.08 to a 3.10 ratio.
Drifting
Joined: Sep 2006
Posts: 1,259
Likes: 2
From: MS
You can make a pointer for your driveshaft if you need to. There is no 3.23 Corvette ratio, they went 3.08, 3.36, 3.55, etc and you should be able to see the difference between a little over 3 turns and 3 1/3 turns. You could also spin the tire 10 times and then the driveshaft would turn either almost 31 or 33 1/2 times.
Thread Starter
Racer
Joined: Feb 2009
Posts: 343
Likes: 0
From: San Diego CA
It would be slightly more difficult if you were blind, but even then you could tell by your tactile senses. If you know the available ratios, you will have enough information to deduce the result. You'd have a convincing agruement if the distinction was say a 3.08 to a 3.10 ratio.
You can make a pointer for your driveshaft if you need to. There is no 3.23 Corvette ratio, they went 3.08, 3.36, 3.55, etc and you should be able to see the difference between a little over 3 turns and 3 1/3 turns. You could also spin the tire 10 times and then the driveshaft would turn either almost 31 or 33 1/2 times.
I've looked on the Diff. for markings but cannot read any. Driveshaft spin, here we come!
