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Old 03-23-2013, 10:40 AM
e39530i5speed e39530i5speed is offline
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Location: United States
Join Date: Feb 2013
Posts: 5
Mein Auto: BMW/E39/530i
- myself, i'd really not bother screwing around w/ the diff without going to LSD at the same time unless yer on a super tight budget. tossing an E46 or M5 LSD in adds to the ROI for sure.
An LSD is absolutely a pointless waste of money for me. This 540i is a daily driver to get from point A to B...5.3 miles one way. I can get a used open 3.38 for $260 with shipping included and swap it in within a few hours assuming I flanges are compatible. If already checked and the rear cover has the same bolt pattern and uses the same gasket.

Lastly, as any racer will tell you, there's no "right" empirically "better" gearing and despite street urban legend to the contrary, higher geared diffs don't "put more power down", they just put it down at different wheel speeds.
So many people assume that a 540i 6-speed must be tracked or some sort of performance machine. Its just a daily driver LOL. I'm not trying to race it or do anything that I wouldn't do if I had a Toyota Corolla. A shorter differential ratio will shorten my gearing so I can have power on tap when I need it. I don't mind shifting a bit more often.

As it is right now...take an E46 M3. Its gearing (example of 1st gear) is 24.6% more multiplied than a stock 540i. In 1st gear, a 3.38 will yield me less 20% more multiplication. So my gearing will still be taller than any stock E46 M3. Not that bad if you think about it. 1st gear will still be plenty useful while 2nd-4th will provide phenomenal traffic drivability and passing power. For highway, 6th gear will keep the engine way below 3000rpm anyway.

And lastly, it will make it a lot more fun!
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