What's the difference between 3.15, 3.31, 3.55, 3.73 TORSEN limited-slip rear axles?

Been trying to build a nifty 2016 Mustang GT Premium Fastback on Ford's website, and can't quite understand the difference in the available options for the limited-slip rear axles. Can someone explain the difference between the sizes I listed or what it means if the size is higher vs lower.

Thanks in advance.


1 Answer 1


Gear ratio is the only difference.

3:73 to 1 is the lowest ratio which means it will be faster in the short run, stop light to stop light.

3:15 to 1 is the highest gear ratio which means it will be faster on the top end, highway.

The first number means how many revolutions the drive shaft turns for one revolution of the rear wheel.

The higher the first number is the Lower the gear ratio is, which means it will have faster acceleration on the low end (stop light to stop light).

Depending on how much Horsepower you have what these numbers actually mean in performance.

  • So if I was getting a Mustang for every-day use which would you say would be better? Aug 27, 2016 at 1:28
  • If you are not racing get the 3:15, which is better MPG.
    – Moab
    Aug 27, 2016 at 1:34
  • 1
    That's a subjective statement, Moab. If the operator is using the vehicle strictly for in town driving, the higher (numerical) ratio will get better gas mileage. It also depends on whether the vehicle is a manual and what the final overdrive ratio is for that gear. There are a huge amount of factors here you haven't taken into account and have thrown out a generic answer which could be improved upon. Aug 27, 2016 at 12:33

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .