What exactly does 4:10 mean??
 

When peopel say they have 4:10's or 3:73's what exactly does that mean. I know it is gears but.... what exactly is it and is it true that is you dont have a lot of power that it can mess up your car. Cause all i have right now is a SLP loudmouth

Gears are a torque multiplier that change the ratio of your rear end. The higher up the number, the shorter each gear is. essentially they get you up to your powerband quicker.

A lot of people say that gears are the first mod you should get...you can slap gears on a stock car and be fine.

Gears with alot fo tires wont mess up your car, it's just people dont put high # gears w/ a supercharger, because with say 4.10s and a Kenne Belle you just have a really expensive tire burner. So basically with high gears, and high torque of a S/C you get no traction off the line. But with a turbo you could even go 4.30s or 4.56s...because with a turbo, the power doesnt kick in untill a certain RPM

To actually answer the question, the number is an expression of the ratio of the number of teeth on the ring gear versus the pinion gear in the rear end. Count the number of teeth on the ring and divide by the number on the pinion and you have the gear ratio. A higher number means that the wheels turn farther in relation to driveshaft speed, therefore making the car faster. With 3.08 gears the rear tires turn 3.08 times for every time the driveshaft turns. With 4.10's you get an extra turn of the tire for each revolution of the driveshaft.

Got it?

glad some answered that correctly. but if you want an easier way to estimate what your ratio is that you currently have you can just jack up your rear end, block the front tires, put it in nuetral and have a buddy spin the rear wheel by hand, while you watch the drive shaft. 3 1/4 turns of the tire for one turn of the shaft means you got 3.27's ( the stock GT gear).
at least this way you dont have to open the rear.
this is also a good trick when racing for $$$ that way you know if the guy says i got a stock stang. you can make sure hes got no gears in it.

gears
 

actually, you guys have it backwards...
the ratios are #.##:1.
for example, w/ 3.73's, the driveshaft rotates 3.73 times for every tire rotation. that's why taller gears increase torque multiplication.

Ever rode a 10 speed bike?

A 10 speed as five sprockets in the back and two in the front right? Well, think of the 5 in the back as your 5 gears. Now, think of the two sprockets in the front as you rear-end gear ratio. Then, it all makes sense. Going from 3.27's to 4.10's is like going rom a larger front sprocket to a smaller front sprocket. The bike is now much easier to pedal, but you loose top-end.