Gear ratio change?

[Vas]

I picked up a Z4 3.64 differential with finned cover for $25. I did have to swap the flanges, but no issues at all!

What year z4?

I would love to do this and then swap in a clutch pack lsd unit.

[az3579]

What year z4?

I would love to do this and then swap in a clutch pack lsd unit.

I would assume E85 body style, any year of that range... pre-2009.

[wsmeyer]

There's a 3.46 from a 325 on e46f right now if someone is feeling adventurous

http://forum.e46fanatics.com/showthread.php?t=1007697

Only $185.00

[Avetiso]

I have a 3.38 from my parts car.
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[PirateZHP]

Sooo... what do these all really help with? And do you lose 6th gear?

[Avetiso]

Sooo... what do these all really help with? And do you lose 6th gear?

No, differential doesn't affect your transmission directly.

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[Hermes]

Well... it does in a sense. You will gain acceleration with the shorter gearing, but lose some top speed in each gear. You will not lose an entire gear, just speed vs rpm in each gear will change vs now

[az3579]

An important thing to note is that your gas mileage will suffer because of the higher revs at cruising speed. This site will calculate what the revs will be at any given speed:

http://www.bokchoys.com/differential...calculator.htm

This may not matter to some, but just having higher revs while on the highway can be irritating depending on the circumstances.

[derbo]

An important thing to note is that your gas mileage will suffer because of the higher revs at cruising speed. This site will calculate what the revs will be at any given speed:

http://www.bokchoys.com/differential...calculator.htm

This may not matter to some, but just having higher revs while on the highway can be irritating depending on the circumstances.

Im losing 2-3mpg difference with my 3.62. Used to get 29-30mpg consistently, I'm getting closer to 26-28 depending on how hard i drive, which happens more often since I'm in the powerband quite more often..


IMO, as long as the RPM for 70mph in 6th gear is near 3000rpm, you should have minimal impact on mpg unless you drive it harder.

[JupiterBMW]

...70mph in 6th gear is near 3000rpm, you should have minimal impact on mpg unless you drive it harder.

What if your highway cruising speed is typically 85-ish...?