August 15, 2008
These 4.10 gears from Motive were the third modification I had done to my GT. The difference in acceleration was very noticeable. One thing everyone warned me about was a drop in fuel efficiency, which I did not see. The gears allow the engine to operate at a more efficient speed, which won\'t really affect mileage if you keep your foot out of it.
Another common misconception is a drop in \"top speed.\" That is totally false. Your top achievable speed will actually increase now that the engine will be operating at a slightly higher rpm. Sure, the top redline speed is lowered to 156, but unless you can run 8\'s in the 1/4 mile, you have nothing to worry about.
These gears did have a little bit of whine, mostly heard when no load was placed on them (coasting). Unless you hear excessive whine (almost like a loud hum heard at all times), you have nothing to worry about.
I recommend you give these gears a couple of heat/cool cycles before putting the pedal to the floor. That hardens them up.
Lastly, plan things out before you get 4.10s. For an N/A Mustang, they provide a good increase in acceleration at the cost of 500 rpms. If you plan on supercharging your Mustang, I urge you to consider 3.73s.
Overall these are a very good set of gears, and ideal for most Mustang owners. I recommend purchasing the differential bearing kit with these gears.