Mustang Gears: Frequently Asked Questions

In an 8.8” rear (GT) you will need 2.75 quarts of gear oil. A 7.5” rear (V6) requires 2.5 quarts of gear oil. Our Royal Purple gear oil already includes the friction modifier that is required by the manufacturer.

• The higher the ratio, the more pickup you will get, but that is not always best. Typically, we recommend no higher than a 3.73 gear for a Mustang that is a daily driver. It will provide the additional pick-up you are looking for, but will not sacrifice your top end speed and increase your fuel consumption drastically. For drag applications, a 4.10 is the way to go. If you install a 4.10 on a vehicle that is used for a lot of highway driving, you will find that you are unable to reach highway speeds (65 and higher) because of the gearing, and you will also notice a lot more fuel consumption than normal.

*Here is a Gear Ratio/RPM chart to help you better understand what kind of RPMs to expect with different gears.

• 87-93 GT and LX - 8.8
• 94+ GT - 8.8
• 94+ V6 - 7.5

If your car is over or is close to the 30,000 mile mark, your bearings are worn to your old gears. If you have less than 30,000 miles, it is generally accepted that you can install gears using just the install kit and your current bearings. We recommend getting the bearing kit over just the install kit. You will already have everything apart; you might as well install the bearings while you are in there...

To correct the speedometer and odometer reading on your Mustang after installing new gears, you will have a couple options. Depending on the year of your Mustang, the correction can be done by installing a speed calibrator, reprogramming with a chip or tuner, or installing the adjustment gear available through Ford racing.

If you have a Ford Limited Slip Differential on your vehicle, and have noticed that only one wheel is spinning when both are supposed to be, it is time to rebuild your LSD.