In Reply to: 3.46 Differential w/40% lock-up: opinions posted by Joron on February 08, 2000 at 14:52:56:
This is hard to answer correctly since you did not mention what model BMW you are driving. I have a 3.46:1 w/40% lock on a 1995 M3. This is great for the track but not good for the street. You will be tooling around town at high revs. If you have a 95 M3 the stock diff is 3.15:1 the 96+ M3s have a 3.23:1. The latter is a nice compromise between street and highway performance and gives you a nice jump on the start. If you have a 95 I would go to the 3.23 if already have a 96+ then do nothing. Put the money into an underdrive pulley or supercharger.