Submitted by: BAFMustangGT & Code001
Probably the most frequently asked question on every mustang message board, gears are not debatable. A 4.10:1 ratio minimum, on a daily driven 4.6L naturally aspirated Mustang would be the way to go. I’ll get to why in a minute, but to realize why there is no debate, we must first look at what gears do.
Gears live in the rear-end, bolted to the pumpkin and driven by the drive shaft. The job of gears is to multiply the engine’s torque and transfer that to the rear wheels via the rear axles. So, with a 250 torque engine with 4.10 gears, your multiplied torque will be 1025. You might be thinking, “Why the heck do we need that much torque?” Well, the truth is, without a multiplication of torque, our cars will not move.
Most stock mustangs have 3.27 gears from the factory. I have no idea why Ford put these gears in our cars because they’re awful. Despite what some “experts” might tell you, gears will not decrease your top speed in a mustang; in fact, they’ll probably increase it. If you were to top out your car with 3.27 gears, you’ll notice that the power just stops when you shift to 5th gear. This is because you are not in the car’s power band to pull the car up to higher speeds. Not only will steeper gears allow you to pull quicker, but they’ll also keep you in your power band which will, in turn, enable you to pull stronger in 5th gear; something you could NOT do before. Other experts claim that you will lose gas mileage due to the higher RPMs that your car will now be traveling at on the highway. In reality, you’ll lose maybe 1 MPG at best.
By far, the biggest misconception out there, is that 4.10s are “too much gear” for a car. These people that tell you this are mistaken. Those people are stuck in the pushrod days where the cars can’t rev past 5500 RPMs. Our cars rev to 6000 RPMs for a SOHC and 7000 RPMs for a DOHC. Our torque comes on later than the pushrods, hence the need for the steeper gears. Sure, there are instances where you might want to get a different gear ratio if you have a power adder or are a drag only car, but be it Auto-crosser, Open Tracker, or Drag Racer, do NOT get less than 4.10 gears for a daily driven N/A Mustang.
When making the leap to a higher gear ratio, consider getting a posi-traction or limited slip differential installed at the same time as the gears in order to save time and money. You will also need an instillation kit, and it is always a good idea to replace your axle seals in the process as well. As always, ensue that you do not have a posi rear end first before ordering one of these units. This will depend on your Mustang’s year and model.