*!!!MUSTANGTUNING's OFFICIAL GEAR THREAD!!!*

[MattJ]

Ok we all got sick of seeing these gear threads so this is THE official gear thread of gear threads. This should tell you mostly everything you need to know with gears. If a question you have, isnt answered in here ask and if it was and you post it, I will delete it because you are stupid.

What is the right gear choice for me?
Most people will tell you to go with 3.73s for v6s, 4.10s for 2v v8s, and 4.30s for 4v v8s. This is usually recommended for all Naturally Aspired engines, and even for the Forced Inductioned 03-04 Cobras. Nitrous injected, and supercharged, turbocharged vehicles usually yeild better results with smaller gears. There are countless ratios of gears available for vehicles but the most popular for us are 3.27s, 3.55s, 3.73s, 3.90s, 4.10s, and 4.30s. The numbers represent the ratio of the gear teeth to the pinion gear in the rear end. You can find this number by counting the teeth on the ring and dividing that number by the number on the pinion and that will be the gear ratio. The higher the number of the gear ratio, the more times your driveshaft will rotate per wheel rotation. 3.73 gears will rotate your driveshaft 3.75 times per one full turn of the wheel, and 4.10 gears will rotate a tad over 4 times per turn of the wheel. This is essentially a torque multiplier. With changing gears your rpms will change in each gear you are in, and I suggest looking at a gear calculator for your vehicle to pick which gear is best suited for you.
Gear Calculator : http://www.tchracing.com/tech/gearcalc


What is needed for the installation of gears?
There are a few things that are needed to complete the installation of new gears. First you need the ring and pinion with the ratio of your choice IE 3.73s, 3.90s, 4.10s, ect. Secondly you need 2 quarts of gear lube. I suggest a fully synthetic lube. Some have Friction modifier in it, and some dont. If its not included youll need it to help prevent your gears from "chattering." You will also need a rear end bearing kit, or installation kit depending on the mileage and year of your mustang. If you have a car with higher mileage or you are just picky or have bad luck, id say go with the bearing kit. If not the install kit is fine for most people. You will also need either a reprogrammer to make up for the change in gears or the dallas speedcal to fix your speedometer because gears will throw this off if it is not fixed correctly. Lastly, you need someone with the knowledge and the tools to do the installation right. If you ask "whats involved in installing gears" than chances are, you cant do it. Have a professional do them for you. The price should range for the average consumer around 100-250 bucks, all said and done.

Note: If you have a 1998 and prior car you do NOT need a Speedcal or a Reprogrammer. Your speedometer is mechanical, not electronic. Therefore, you need to get the proper speedometer gear to match up with your gear choice. You can find speedometer gears, here:

http://www.steeda.com/store/-catalog/speedometer.htm

-Shambles

What do I get out of different gears?
As mentioned above, gears are a torque multiplier so it would feel like some soft of power adder was put on your vehicle. Most people can yelid on average of .5 seconds off your 1/4 time simply by changing your gears. You will also notice a lot of the serious mustang racers and NMRA racers with 4.30 gears are capable of putting themselves in the high 12s, with minor bolt ons, weight reduction, and drag radials, so that gives you an idea of what gears are really capable of with a good driver.

[MattJ]

Here is a picture walk-through of the gear installation method. It is NOT recommended to intall gears by yourself but this gives you a BASIC idea of whats ahead for you and the work involved.

picture 1: Pull the rear end cover and crack the bottom open to let the fluids drain out.


picture 2: Carefully pull the ABS sensors, and pull the axles after they are disconnected.


picture 3: Unbolt the tlock and ring assembly with the 4 bolts. Pull the unit out.

[MattJ]

picture 4 5 6: Unbolt the driveshaft because it is attached to the pinion. have the pinion held on the other side so it doesnt drop to the ground and get damaged. Remove that as well when its disconnected from the driveshaft.

[MattJ]

picture 7 8: Install the ring gear back onto the tlock assembly and resinstall back into the rear end.




And thats it. Now, remember. This is only the basics of the gear installation process. This does not include measuring shims for tollerances, removing tires, brakes, c-clips inside of rear housing, and all the other stuff that doesnt need pictures taken of. This was the installation of Motive Performance 3.90s in my personal vehicle. Please feel free to donate money for my time.

[MattJ]

Topic is now open for discussion. Please stay on topic or I will be forced to beat you to death with my 3.27s.

[Lightning247]

I would concur completely with the gear recommendations above. The only things I would add is that if your 4V car doesn't see alot of highway time and you're serious about running well at the track. I would get 4.56 gears. This is the standard for anyone seeking max performance at the track.

The other thing would recommend is if your running a positive displacement blower (really only for 03/04 guys) I wouldn't run more then 3.73 gears. These 03/04 Cobra cars especially modified have enough traction problems as it is esp. on the street. Therefore you'd want to keep the Gearing close to stock if youre anywhere near the 500rwhp range (are there any 03/04's that aren't? )

Other than that this is a great thread!

DON'T FEAR THE GEAR!

[csledd]

very nice article. I had a ton of pics from my install I could've contributed but my hard drive crashed


the gear oil smells TERRIBLE.

[i love soccermoms]

sooo why wouldnt you put 4.10's on the v6?

[Lances03SVT]

I'd say it would make it top out way too fast.

[Grimmz]

I did some of the calculations with that calculator MattJ posted, how come my v6 is said to run better with 3.10 gears rather then 3.75 gears that they recomend? do they even make 3.10 gears?

[Shambles]

If you are wondering what gears do read the following.

Originally Posted by csledd

Gears mulitply your engine's torque to get the car up to speed easier. Without gears to mulitply the engines torque, you will never be able to get your car to take off from a stoplight. Gears are numbered as a ratio, for example 3.27:1. This means that the drive gear (pinion gear) must rotate 3.27 times for the driven gear (ring gear) to rotate once. Let's look at some math to better illustrate this. A stock Mustang GT weighs in at about 3500lbs, its engine has a horsepower rating of 225hp and a torque rating of say 300 lb./ft of torque. Without gears your engine only making 225hp and 300lb./ft of torque will have to try to move a 3500lb mass. That simply isn't gonna happen. Now lets see what gears can do for us. Your typical Mustang has a first gear ratio of about 3.3:1 (in the 96-up cars.) So by taking it's torque of 300*3.3, you now have 990lb/ft of torque to help your car take off. That's still not enough to make for trouble free take-off's. Now take that number and use rear-end geras of say 3.27:1 to mulitply that onto the wheels you now have 3237lb/ft of torque to accelerate you. While this is a healthy number, its still less than your car weighs. Let's see what happens when we install say 4.30:1 gears to the car with 3.27's 300*3.3*4.30=4257lb/ft of torque! That's over 1000 lb/ft of torque, 1020lb/ft to be exact that will help your car off the line. This means less bogging, and a car that is extremely fun to drive. By this example, you can see the advantage of a numerically higher gear ratio.

[blue2004gt]

Originally Posted by Grimmz

I did some of the calculations with that calculator MattJ posted, how come my v6 is said to run better with 3.10 gears rather then 3.75 gears that they recomend? do they even make 3.10 gears?

they do make a 3.08

Originally Posted by Lances03GT

I'd say it would make it top out way too fast.

Is that a bad thing?

SO....
What are the possible downsides of throwing 4:10's in an 04 GT besides a slight loss of fuel economy?

I know this will void the crap out of my warranty, im tempted to see if i can sell my warranty back to ford, or i could just keep quiet about it.

so why would this void the warranty? what is this going to wear down and break prematurly?

I totally want to give my car a little kick in the seat of the pants, this looks like the best way to do it.

[MattJ]

Originally Posted by slappy

SO....
What are the possible downsides of throwing 4:10's in an 04 GT besides a slight loss of fuel economy?

I know this will void the crap out of my warranty, im tempted to see if i can sell my warranty back to ford, or i could just keep quiet about it.

so why would this void the warranty? what is this going to wear down and break prematurly?

I totally want to give my car a little kick in the seat of the pants, this looks like the best way to do it.

You shift a lot more but you get yourself into 5th in a lot of daily driving. Chances are they CAN void your warrenty but they probably wont if they arent gonna be dicks about it. its not going to break unless its installed wrong.

Originally Posted by MattJ

You shift a lot more but you get yourself into 5th in a lot of daily driving. Chances are they CAN void your warrenty but they probably wont if they arent gonna be dicks about it. its not going to break unless its installed wrong.

Its an auto.

Im totally gonna do this. I think im gonna buy a winter beater before i do this, i dont need 4:10s in a rear wheel drive V8 on snow.

So if gears work as a torque multiplier, would you see a torque gain on the dyno?

[MattJ]

Originally Posted by slappy

So if gears work as a torque multiplier, would you see a torque gain on the dyno?

Nope. You wont see any gains by adding gears.

Originally Posted by MattJ

Nope. You wont see any gains by adding gears.

So, Same torque, just a shifted powerband.

[csledd]

You will most likely see a DECREASE of HP on the dyno (depending on the dyno setup). The reason for this because you are using a torque multiplication the RPM is met faster before the horsepower actually has a chance to overcome the rotational mass, which is the dyno itself. I guess it's kinda like it revs up too fast and the horsepower is used in keeping it spinning.

Usually it's a 1-5 rwhp loss

[Badfish]

What matt said about 5th in daily driving is 100% true.

I'm in 5th gear goin 45..well the gears AND if I stay in 4th gear my exhuast deafens people

but yeah, I pretty much use 5th gear everytime I drive

[ModMotorRacer]

Don't wanna steal your thunder but you most certainly DO need a speedcal in a 98 and older car. The different tooth tranny gear does not fix the speedo problem, especially in an automatic.

Adam