Hi Rob, Great articles and photos, thanks so much , I have a 1994 BMW 318is. It gets great gas mileage and would love to get even better mileage . The rear end (3rd) member locked up when I first got the car, so I found a deal on a 325 axles and rear end , put it in never changed any gears do you know if the 325 is different than the 318is both were manual transmissions. Should I leave well enough alone ? Thanks, FAN Hello Fan and thank you! I found this excellent website that lists a LOT of BMW gear ratios, perhaps all of them: http://www.bokchoys.com/differential/GearRatios.htm It seems that you now have a less-aggressive final drive ratio of 3.15 vs. 3.45. So if you like your mileage and the acceleration is adequate, I would leave it alone and congratulate yourself on a fuel saving modification. I wouldn't suggest trying anything numerically lower than 3.15 such as the 2.93, even if you can find it. My concern would be inadequate acceleration with the 4-cylinder engine. This wou...