Abuzah

So I was reading on howstuffworks about rear end gears. Now I was always under the impression that a higher gear ratio, ie 4.10's over 3.23's, have more teeth. But the article on the website got me thinking... if the gears in the differential - the ones not attached (are they attached?) to the driveshaft - are changed with gears that have more teeth, wouldn't this slow down the rotation of the axle, as the gears on the driveshaft remain the same? Basically my question is this: when you up the ratio in the rear differential, does that mean you are increasing or decreasing the amount of teeth? And if anyone could give me a simplified explanation of exactly why (my mind has a hard time contemplating this) that would be just great. Thanks guys!

shoebox

If you were to only increase the ring gear teeth, the ratio would go numerically higher.

You have to consider the ring and pinion in pairs, though. It is the ratio between the ring teeth and pinion teeth that give you the numbers. The gears can come in lots of different diameters in different rears, so the number of teeth can be quite different, but the ratio between them can end up being the same.

Abuzah

Thanks for the reply. I'm still kind of confused, however, on how the whole thing works. So is the pinion gear what's attached to the driveshaft? And you change only the ring gear when you change the gear ratio? Or do you change both the ring and pinion gears, but the pinion gears are not attached to the driveshaft? Sorry, I guess I have a bit to learn about rear ends...

shoebox

The pinion is "attached" and inline with the driveshaft by means of the pinion yoke. The ring gear would rotate in the same manner as the rear axles and wheels.

The gears are always matched and installed as pairs. You never change one without the other.

Abuzah

Excellent, thanks for helping me out Shoebox.

djk19

THE chevy gear ratio info:

If you can count the teeth: divide teeth on ring by teeth on pinion:

41/12 = 3.4167 or "3.42" Ratios aren't always exact, except for combinations like 41:10

popular combinations:

41:15 = 2.7333 (2.73)
41:14 = 2.9286 (2.93) not that popular
40:13 = 3.0769 (3.08)
41:13 = 3.1539 (3.15) C5 automatic performance ratio
42:13 = 3.2308 (3.23)
41:12 = 3.4167 (3.42)
41:11 = 3.7273 (3.73)
41:10 = 4.10

GM liked 41 teeth!

This is how the cookie crumbles for our cars. If you were to go to a FORD 9 inch... or a 12 bolt rear you would have LARGER DIAMETER ring gears and probably slightly larger pinion gears. To make the same ratio and be that alrger size you would need more teeth and visa-versa.

The acutal number you hear when you think of the gear ratio is the number of times the engine spins VS. how amny times the rear end spins once.

Ponder that.