Im generally new to the car mod world, i just got my mustang about 4 months ago and it seems that everyone has 4.10 gears, what exactly are they and what is the benefit of having them? sorry if this sounds stupid but i have to ask.

 

It is your rear end Gear ratio. And the numericaly higher is actually a lower gear raio and this adds low end torque but takes from the top end speed. and the 4.10 is the most popular for short sprints.

 

So, if you install them your top speed will lower dramatically? so they are only good for something like a 1/4 mile?

 

it will bump your rpms about 400 rpms, your car still isnt going to top out even with 4.10s, you dont have the power, and you will loose 1-2 mpg highway

 

The lower gears(numerically higher) increasetorque at the wheels by providing more mechanical advantage, but reduces the maximum speed in each gear, and possibly lowers overall top speed(depending on setup). For example my car has about a top speed of 145mph with a 3.00 gear(4 speed manual), and with a 3.80(a pretty big jump for a street car) would have a top speed of about 120-125, but would gain about a 25% increase intorque at the rear wheels. Gearing works with increased hp at higher rpms to keep your speed in gears appropriate yet increase torque at the driving wheels. That being said, most factory gearing is setup with economy in mind more than performance, so a bump up in gearing isn't a bad thing at all for performance and still retaining drivability. Also lower gears(numerically higher) will make your tires wanna lose traction easier, especially in first gear, so a slight change in driving habits is needed to maximize their potential(ie if you spin off the line back out of the throttle a bit)

 

Carefull man, If your just looking forA little extra torque you might look at the 3:73's.I put the 4:10's in my car and freaked out becuase i thought the motor was turning too many r.p.m's.I think it will be ok, it just seemed like alot more. It took away from my top end andI kinda wishI had went with something a little less dramatic. Dont forget youll have to get a tuner to fix your speedo it'lla few m.p.h's off too. By the way whileI'm here maybe some one can tell mewhat 55 is with that kinda change,I rode around at 80 m.p.h. for untilI got tuned correctly butI was clueless. Anyway at 60 m.p.h. my car turnes approx 2600-2800 r.p.m.'s, so run your car to those r.p.m.s and see what you think before you make any changes.

 

don't fear the gear , 4.10's rule , you'll think you just added 100 horsepower to the car.

some people will act like 4.10's as opposed to 3.73 will knock top end down by 20 mph, and rpms will raise 1000 and it's just not true.
you will tach about 250 more rpms over the 4.10, about 250 for every gearset you step up, so if you had 3.08 you will tach about 1000 more w/ 4.10's

it puts you in and keeps you in your powerband.

i tach w/ my '93 5-speed and 4.10's 3000 doing about 85, and get 21 mpg w/ no ac running

my old '89 w/ 4.10's and tires went 13.50's w/ nothing else at all.

on a 26" tall cheater slick, 3.73's just don't have enuff leverage for a nice launch, much better than stock, but still not enuff

 

I just read this post on the forums now and just to let u guy's know thanks for all the info on those gears. i was also wondering what the bennefit of the 4.10s were. i have a 89 lincoln mark vii but has the 5.0ho 302 in it would the 3.73s or 4.10s work better in the rear end for it i know matters bout weight also . but im guessn my car is heavier then a foxbody

 

Oh yeah^

Finally someone noted out that gears DO NOT INCREASE hp/torque...but they put you into your car's powerband faster, therefore getting more pickup. This can lead to INCREASED top speed by gears...depending on the car.

There are 3.90's out there too...why do I never hear of them? Are they BAD gears? I suppose not. The 3.90's would seem to be the most logical choice, IMO...not too much/little.

The higher gear will give you poorer gas milage...depending where you drive. If you drive over 65 mph on the highway most of the time, a 3.73 gear would do you fine. 4.10's are for short runs, but you can still get good speed, despite what most people say..