not my doing... MattJ's over at www.mustangboards.com 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. 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. 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. 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.