[blackedout330i]

Originally Posted by 72GMC

BlackedOut,
I'm also new to E90 330i ownership, and have been looking into diff swaps.

The 3.46 ratio might not be compatible without changing the driveshaft. And it's really a "mild"change.

I'm leaning towards a 3.64 ratio, which I would classify as "moderate" option

Next option is the 3.91, an "aggressive" choice that many seem to be happy with.

In my old 328i E46 I went from a 2.93 to a 3.46 (18%)and it was hella fun. I believe our 330i has a 3.15 and going to a 3.46 would be a 9.8% increase. Not much, but assume it would be nice for highway MPG. A 3.64 diff would be a ~15% change. I would say the 3.73 would be the "poor mans supercharger" and thats would I would recommend (~18% change).

When I had a UUC stg2 8.5LB flywheel, paired to a 3.46 in the E46 I have to believe i dropped near a second to 60mph. Any gear, and I mean ANY gear, had plenty of thrust and I was still getting around 30mpg highway. Very fun.

Im a week or so from installing a JB RACING lightweight flywheel and eventurally finding that 3.73 diff to get that performance feel my E46 gave me. Dont get me wrong, I love the 330 but I just want more "fun".

[3PedalJake]

Originally Posted by blackedout330i

In my old 328i E46 I went from a 2.93 to a 3.46 (18%)and it was hella fun. I believe our 330i has a 3.15 and going to a 3.46 would be a 9.8% increase. Not much, but assume it would be nice for highway MPG. A 3.64 diff would be a ~15% change. I would say the 3.73 would be the "poor mans supercharger" and thats would I would recommend (~18% change).

When I had a UUC stg2 8.5LB flywheel, paired to a 3.46 in the E46 I have to believe i dropped near a second to 60mph. Any gear, and I mean ANY gear, had plenty of thrust and I was still getting around 30mpg highway. Very fun.

Im a week or so from installing a JB RACING lightweight flywheel and eventurally finding that 3.73 diff to get that performance feel my E46 gave me. Dont get me wrong, I love the 330 but I just want more "fun".

On my '06 330i I swapped the 3.15 diff for a 3.64 from a 330i automatic and it feels just about right IMO. It's a direct swap, no other changes needed it bolts up to the driveshaft. Plenty more perceived torque, highway passing is easy without downshifting but not so much of an change to make it feel buzzy or high strung

[blackedout330i]

Originally Posted by 3PedalJake

On my '06 330i I swapped the 3.15 diff for a 3.64 from a 330i automatic and it feels just about right IMO. It's a direct swap, no other changes needed it bolts up to the driveshaft. Plenty more perceived torque, highway passing is easy without downshifting but not so much of an change to make it feel buzzy or high strung

What's your highway mpg

[3PedalJake]

Originally Posted by blackedout330i

What's your highway mpg

I haven't separated highway from general use. It didn't change after the swap, hovers just above and below 26mpg on the monitor screen.

[72GMC]

Originally Posted by 3PedalJake

On my '06 330i I swapped the 3.15 diff for a 3.64 from a 330i automatic and it feels just about right IMO. It's a direct swap, no other changes needed it bolts up to the driveshaft. Plenty more perceived torque, highway passing is easy without downshifting but not so much of an change to make it feel buzzy or high strung

Thanks for sharing,
The 3.64 might suit my intentions perfectly.

I'm looking at this spreadsheet, trying to determine if it translates to the E90.

http://diffsonline.com/images/GearingCalculator.xls