[Chris1337]

How much torque do I lose going from a 3.46 to a 3.15? Currently at 458 wtq
Putting a e92 m3 lsd on my 335i and want to know what numbers look like

[desertman123]

1) you're in the NA forum
2) it's more complex than you think.

Your motor will always be able to produce 458 ft-lbs of torque (for simplicity sake I'm not converting wheel horsepower to crank horsepower).

What you're changing is your mechanical advantage - your torque multiplication. Think of it like a lever, or a breaker bar. The longer your breaker bar, the more the force is multiplied.

For example, YOU as a person will always apply that 100 lbs of force. But the force that comes out on the other end is now changed. If you have a 1ft breaker bar, the torque to spin the bolt will be 100ft-lbs. But if you have a 3ft breaker bar, the torque to spin the bolt is now 300ft-lbs.

Going from a 3.46 to a 3.15 ratio diff is going to feel like you lost approx. ~10% of your torque.

BUT your RPM at any given speed will now be ~10% lower. Let's say you were at 3000rpm in 4th gear going 50mph. Now you'll be at 2700rpm in 4th gear going 50mph. So your top speed in any gear will be higher.