What are the cost benefits of going from a 2.81 gear to a 3.15?
Going from a 2.81 to a 3.15 will reduce gas mileage by 1-3 miles per gallon and reduce your top speed in each gear, but you will pick up more torque. You should reduce your 0-60 time by about .15 seconds and could see a reduction in your 1/4 mile. The reason why the gear change may not reduce your 1/4 mile time is that the gear change will cause you to do an extra shift (3rd to 4th) that is not necessary if you stick with 2.81 gear. Folks believe that it will cut down your 1/4 ET anywhere from .2-.6 seconds. On E39s the gear swap is fairly straight forward.
