A Handy Tool for Considering Tire Size & Differential Ratios

[Darby]

I would only use the calculator instead of inputting all the car info. I know it helped me make decisions while I was building my car.
All the transmissions you mentioned have a final drive of 1 to 1, the type of transmission doesn’t matter. Year, make, and model will also make no difference if you’re only after getting to a certain rpm at a certain speed. You can see how much a taller tire changes the rpm at speed as well as what a gear change would do. You could also see that changing both may be needed to get to a desired rpm at a certain speed.
I hope the website can help someone as much as it helped me!
As for the correct gear on the speedometer cable to show the correct speed, that’s something different. I know I’ve purchased a few to get that right in the past.

 

[edbods]

I don't mean to tread all over your efforts Gerald, but Blocklayer has a really nice gearing calculator. You can also input gear ratios individually, or select gearbox presets from the dropdown list (I asked the admin to add the 727 ratio although it was actually already there as 'Dodge TF727'). You can even input your tyre size and it'll tell you the diameter, either in metric or imperial units. If the preset list doesn't have a gearbox you're looking for, just let the admin know via the link on the same page.

It has a whole bunch of calculators, ranging from things like stairs (straight, spiral etc.) to a belt pulley length and rpm calculator, there's calculators for things I didn't even know existed lol, you can check them out here.