Gear ratios

Q; I’m trying to figure out what the rear axle gears, or ratio is in my Galaxie, do you have a simple way to determine this?

A; This is one of those details that many don’t know, or need to know, until they entertain the thought of a better performance from the final drive. And there are those of us that are tried and true gearheads with 90 wt in our veins that keep this info in our heads, but forgot what we had for dinner last night.

We won’t get into the teeth counting, and calculating stuff that a mechanical engineer would prefer to do, there is a much easier way to closely determine what ratio you have.

Set the rear tires off the floor with jack stands, one of the tires will be marked on the inside corner of the tread with masking tape, also mark the driveshaft. You will set the marked tire with the tape at the 6:00 position, then mark the driveshaft on the 6:00 position. The opposite tire will need to be held in place, assuming that you have an open spool rear.

Now rotate the driveshaft and count the # of rotations it takes to rotate the tire 360’. Ex; if it takes roughly 3 turns of the driveshaft to get one on the tire, your ratio is 300:1, that one is a common one for the Galaxie. If it takes 3 ½ turns of the driveshaft to get one on the tire, you have a 3.55:1 ratio, and so on. Gearing the rear to allow the driveshaft/ pinion shaft to rotate more per rotations of the axle gives you more off the line power, but you will lose highway cruising speed capabilities.