Modern technology has left many of us with some easy tasks. These days when you upgrade the ring and pinion gears in the rear differential on your late model Mustang, chances are you make a change using a hand-held tuner so the computer sends the proper speed signal to the speedometer in the dash.

It used to be a little more complex of a job tough. Fox-bodies and 94-95 SN95 Mustangs used a speedometer cable, which connected to the transmission and had a driven gear that spun. This mechanical link drove the mechanical speedometer in the dash. If you changed rear end gears you had to consult a chart at your local Ford dealer parts counter to figure out what gear you’d need.

Since speedometer gears are a thing of the past, so are those charts, and in many cases the parts professionals selling the gears are long gone or at best have foggy memories of which gears were used. LateModelRestoration.com is once again coming to the rescue with their new Speedometer Gear Calculator tool.

This online tool is easy to use, and is designed to take the guesswork out of picking the correct speedometer gear. All you need to know are a few basics from your car to select the right gear. Those items include the transmission type, the new rear end gear ratio, tire width, series, and wheel diameter. You’ll also need to know the drive gear teeth. The drive gear is the gear located inside the transmission on the transmission output shaft. These aren’t easy to change, and are typically only swapped out during a rebuild. On automatic transmissions they can’t be changed at all.. A guide is included as well to help users easily identify which drive gear should be inside the transmission.

Regardless, plugging in the correct information will tell you what gear you need, and LateModelRestoration.com even brings up the part, part number, pricing, and link to buy it when you do the calculation. Along with the calculator LateModelRestoration.com includes a video on how to use the calculator and change the gear. For those of us still working on Fox-body Stangs this is one more easy tool, that is sure to get a lot of use, and prove invaluable over the years. You can check out the Mustang Speedometer Gear Calculator tool at this link, and order your gears from LateModelRestoration.com while you’re there.