I doubt you could calculate that because of too many variables. It should be possible to take the torque and power curve to make an estimate using the F=ma solved for a: a=F/m.

If you take a plot of the torque curve v RPM that is the same as Force (force*length=torque. Length stays the same so force can interchange with torque)

If you use the ratio of the two different rear ends you will get a value such as 1.2. You would plot a new torque v RPM to determine the increased @ wheel torque (it will be the equivalent of the engine having more torque)

The speed of the car drops by the same ratio. You would have to factor that in.

You could either make plots and do the math to figure out the actual acceleration at say every 1/10 of second. Reverse engineer the actual force applied to get your car to 60 based on actual tests performed.

Once you have the actual force from each 1/10 s figured out, you multiply that by the differential ratio ratio to make a new curve. Then calculate a new set of force values every 1/10 s. You could probably get pretty close.

The easier way is to Google search the results of somebody else that already did the same thing. Try to find a similar engine doesn't need to be X5 but maybe heavier sedan like 740.

You will get say 10-15% more acceleration but the gears have to run 10-15% longer which you would think will cancel out. The whole point off a higher ratio rear end is to shift some of the highest effort acceleration into a more torquey part of the power band. The trade off is less power at higher rpm so it's "all about the bass no treble". (all low-end).

It's quite possible you would end up no faster 0-60 but hella faster 0-30.

You can use an app like dash command for aromatic 0-60 measurements it uses the accelerometer in the phone to determine launch and taps into the car computer to know the speed.

I would be very interested to know the results. Oh you will surely get lower mpg keep that in mind.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)