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.

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.

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?

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.

Hmmmm. :) you think a 3.64 will still go like hell and maybe get me to 155 or 60? Hehe.

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.

What do you think I should get? 3.64 or 3.73?

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!

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.

Well I'm hoping to find a 6 speed when I do my swap at some point.

Thanks though I'll fiddle around with that website some!

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.

Well I haven't looked much through transmissions yet.

If i were you I would hammer that out first because it might affect your diff choice.

For now I'm all stock.