M42 and gearing

[HighschoolE30]

So my 318is has the factory 4:10 LSD in it still. Its great for getting up and moving, but going down the highway its running pretty hard.

Has anybody else ran a lower ratio? Does the m42 need the 4:10's? and would the MPG increase be worth a swap?

[Ryann]

http://www.r3vlimited.com/board/showthread.php?t=189655&highlight=m42+diff+ratio

[Dj Buttchug]

i run 2.93 its nice

[KenC]

i run 2.93 its nice

With a turbo. A 2.93 on an NA M42 is an absolute joke.

[bmwm42]

I agree 2.93 seems hella useless on a m42 3.64 would be as low as I would go

[SimplyDope]

Paired with a MarkD chip, I found the 3.73 to be a great all-around setup. I daily drive mine with a healthy dose of highway driving and downtown traffic. I went from a 4.10 open diff FWIW.

[Bearmw]

I imagine a small 3.90 limited slip would work well. The smaller ring and pinion takes less energy to turn than a larger one and the diff itself is 20 or so pounds lighter. Actually I think the small 3.90 is an ideal diff to run on a stock or near stock M20 (with a light flyweel and chip).

[bmwm42]

I imagine a small 3.90 limited slip would work well. The smaller ring and pinion takes less energy to turn than a larger one and the diff itself is 20 or so pounds lighter. Actually I think the small 3.90 is an ideal diff to run on a stock or near stock M20.

no one cares about the m20 m42s ftw.

[Balleristic31]

I want 4.45

Oh wait you want your car to feel slower :(

[Dj Buttchug]

With a turbo. A 2.93 on an NA M42 is an absolute joke.

very true.

but NA with 293 you can approach 40 mpg... in 4th gear cruising lol