Project MILF 2006 Ford Mustang GT Gear Install - Fueling Around - Tech

A wise man once said that when you reflect on your marriage and remember happy times, it's how you handle the rough patches that allows your marriage to stand the test of time. The same can be said for a family project car. Being able to deal with the ups and downs of adding parts on your car for the sake of increased performance is crucial to keeping your sanity.

Case in point is this month's installment featuring our '06 Legend Lime Mustang GT, Project MILF. Let's recharge the batteries for a moment and bring you up speed as to where our beloved Mustang lies. What started out as a bone-stock, automatic transmission-equipped S197 GT has been transformed in a series of stages. We began with the installation of the Ford Racing Performance Parts Handling Pack before lowering a Whipple supercharger and accom-panying FRPP Super Pack parts on top of the Three-Valve mod motor. We then ditched the factory exhaust for a set of Stainless Works long-tube headers and a full-on exhaust system.

This month, we decided to go down what we thought was the easy route and ditch the stock 3.31 gears in the Stang's 8.8-inch rear, replacing them with a more aggressive 4.10 gearset. With a best elapsed time of 12.47 seconds with the highway-friendly 3.31s, we figured by putting in the 4.10s, the car would get out of the hole quicker at the track and we'd drop e.t. in the process. The numerically higher gears allow the car to 60-foot better, as well as climb through the rpm range quicker due to their offering a greater mechanical advantage. Also, the 4.10 gears would let the engine achieve a higher speed going through the traps, thus keeping the motor in the sweet spot of maximum horsepower production.

We once again piloted the retro-Stang to Crazy Horse Racing, where mechanic Glen Knell handled the chore of swapping out the gearset. Before we set upon swapping gears, though, we realized that once the 4.10s replaced the 3.31s, the computer would need to be recalibrated to accommodate the lower gear ratio. If you don't recalibrate the computer for the new gears, you can actually cook the clutches in the transmission. The vehicle speed sensor will operate with the mindset that the car still has 3.31 gears in the rear instead of the 4.10s. The engine may also rev so much more quickly that it will hit the rev limiter before the computer commands it to upshift. With the vehicle speed sensor being off when compared to the actual vehicle speed, upshifts and downshifts of the transmission will also be erratic, and hard driving or extended periods of cruising will cause the clutches in the trans to overheat and eventually fail. With that in mind, we picked up the telephone and had tuning guru Job Spetter Jr. of Turbo People meet us at Crazy Horse to help us with the tuning aspect of the car.

While the actual gear swap itself was fairly straightforward, we ran into a bit of difficulty tuning the car. According to Jesse Kershaw at FRPP, there is a recalibrating service offered where you can easily recalibrate the computer when you swap in the gears. "You fax us information with your new gear ratio and we overnight you a new calibrator," he says. "Once you load the tune in, you mail back the old tuner."

The recalibration service is $75. Added into the cost is the $250 core charge that, once the original tuner is returned to FRPP, is credited to your charge card. The problem is the tuning service isn't available for those who put the FRPP Super Pack on an automatic car like Project MILF. With FRPP not having a way for us to recalibrate Project MILF's computer for the gears (at this time), we were forced to have Spetter create a custom tune for the car.