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Old 07-24-2012, 12:26 AM   #1
Breticus
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Default What LSD ratio?

I have a stock M42. I bought a 2.93 LSD with half shafts for a great deal, and I know I'm going to want to change the ratio. So what ring and pinion gear set should I buy? 3.73? 3.91? 3.64? Please help me out. Haha.
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Old 07-24-2012, 01:47 AM   #2
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Any of those ratios will be giving up top end speed and gas mileage for acceleration. The higher the number the more top end and mileage you give up. I would leave the 2.93 in, but that's just me. No BMW was designed with brute acceleration in mind. That's an American thing.
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Old 07-24-2012, 03:18 AM   #3
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What do you think would be best if I have a 6cyl swap in mind in the future? Like s52 or 2.8? I think I'll do the 3.64 or 3.73. If I don't like the top end I'll still have the old gear set to throw in. Anybody else have input?
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Old 07-24-2012, 04:25 AM   #4
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I have a 3.73 in (S52 with some goodies) I love it cause it goes like hell and will do about 150 or so at redline. That's plenty fast for me in crowded northern VA.
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Old 07-24-2012, 04:31 AM   #5
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Hmmmm. you think a 3.64 will still go like hell and maybe get me to 155 or 60? Hehe.
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Old 07-24-2012, 04:36 AM   #6
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Yea, it'll pull pretty dern hard. You'll have to get used to the high rpm's on high way but it's tolerable.
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Old 07-24-2012, 05:03 AM   #7
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What do you think I should get? 3.64 or 3.73?
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Old 07-24-2012, 05:30 AM   #8
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I think I'll go with the 3.73 because I tend to like to downshift a lot, and I'm a sucker for brutal acceleration and seeing as I don't think I'll ever have enough road for 160 I think 150 will make me plenty happy and if I ever want super top speed I still got the 2.93 THANKS GUYS!
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Old 07-24-2012, 12:28 PM   #9
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If you put the ratios into a gearing calculator, diffsonline.com has one, you'll only be able to get to ~125 with the stock 5spd and 3.73. With a 6spd you can get to 150 but those aren't cheap.
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Old 07-24-2012, 12:30 PM   #10
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Well I'm hoping to find a 6 speed when I do my swap at some point.
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Old 07-24-2012, 12:31 PM   #11
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Thanks though I'll fiddle around with that website some!
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Old 07-24-2012, 09:59 PM   #12
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Ratio really depends on the tranny not the engine (assuming you have enough power to move the gears). If you tell me the tranny you are going to use I can post a speed/RPM chart up for you.
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Old 07-24-2012, 10:20 PM   #13
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Well I haven't looked much through transmissions yet.
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Old 07-24-2012, 10:22 PM   #14
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If i were you I would hammer that out first because it might affect your diff choice.
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Old 07-24-2012, 10:23 PM   #15
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For now I'm all stock.
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