This is what I found on the Dinancars.com site under the E39 M5
3.45 Limited Slip Differential
Labor Units: 62.0
Required Products: Dinan Performance Engine Software is recommended for increased rev-limit.
Special Notes: The 3.45 differential is sold on an exchange basis; $1800.00 refundable core deposit required.
Point Value: 2
The shorter 3.45 gearing takes advantage of torque multiplication, lowering the stock 3.15 ratio for a 9.5% increase in torque delivered to the road. The improved acceleration comes with only a minor increase in engine speeds at cruise and no effective reduction in top speed potential. The 3.45 ratio was selected in order to enable the car to attain a speed of 60 mph without introducing a second to third gear shift, which would otherwise slow down 0-60 mph times.
The Dinan 3.45 Limited Slip Differential delivers what is perhaps the greatest "bang for the buck" in terms of improved and more immediate acceleration from the M5.