I am been interested in trading for a gear ratio that provides better gas mileage and easier cruising. I understand that the ratio can be determined from counting the number of teeth on the ring and on the pinion and dividing them.

I have also been told that you can raise the back wheels and mark the drive shaft with chalk and determine the ratio by counting the revolutions of the drive shaft for each revolution of the wheel. This is for car that does not have positraction. Is that true?