how gears work

Hope this helps

With the stock 3.27 gear your mustangs top speed would be something like 230mph in 5th gear, but the only problem with that is that our engines don’t have enough hp to overcome the extremely high amount of wind resistance at that speed. So the engine stops pulling at about 3500 rpm in 5th. This results in our GT’s top speed being 148mph. Now if you have ever seen a dyno graph you will notice that our engines max hp comes at about 5500-5700 rpm. To get you engine closer to its power band so it can overcome the stronger wind resistance you will need lower gears and even with 4.10s the top speed is only going to go up by maybe 5-7mph. As far as a high hp car and to what gear to use: 350rwhp and below = 4.10 for daily driving and just about anything above that go with 3.73 or 3.90 max. The reason for that is, if you had a very low gear on a high hp car all of your hp would just go up in smoke . Hope this helps.

In short:
4.10 in 350rwhp car
4.10 helps you get in a more useable power band for top end
3.73 if you have a monster
Lower gears keeps your car in the power band
Don’t fear the gear