[sekhon]

I just purchased a new to me 230i and I have been considering changing my final drive ratio and getting a LSD while I am at it.

I haven't seen many suggestions in terms of a LSD for the 230i, and was curious if anyone had pondered the idea of going even shorter for the final drive ratio... I know the 230i is already on the higher end with a 3.909 final drive ratio, but what would the consequences of getting something even higher be? I figured since the top speed is already electronically limited, why not get more torque and drop the top speed of the car to something near or even below the electronic limiter...

Please educate me on how stupid my idea is.

Has anyone changed the final drive ratio on their 230i?

What is the consequence of going higher?

Any recommendations on who to go with?

What is this process even like?

[freakystyly]

The only consequence is a proportionately higher rpm in all gears (leading to higher fuel consumption). So if your stock ratio is 3.08, going to 3.46 would be 12% higher everywhere. Requiring more shifts and having a higher highway cruising RPM. Also giving a 12% effective torque increase.

This is how old school muscle cars were so quick and torque-y but had low top speeds.

If you choose to go this route, make sure you or your mechanic purchase the correct differential for your car. Your output flanges and driveshaft may not fit if they were for a 6 cyl.

https://www.1addicts.com/forums/show....php?t=1023285
https://www.2addicts.com/forums/show....php?t=1113986

There's many threads on this if you google it.

I'm thinking of going with 3.46 LSD myself sometime in the future.

[aerobod]

The 230i uses the 188LW diff, Probably Diff Lab in Australia is the best starting point for information: https://www.difflab.com.au/products/...90cd29e0&_ss=r, it looks like 4.44:1 is the lowest ratio they have available that is directly compatible with the 230i spline-input style 188LW, which can then be combined with a suitable LSD, that they also sell.

You could then take the parts to a local diff specialist for conversion of your existing diff (ensuring you also have new input shaft crush washer, side bearing shims and new seals). You probably won't be able to recode to adjust for the speedometer changes, but having a new face screen printed by a specialist instrument cluster rebuilder could take care of that. If you have a sat nav built in, the speed input for dead reckoning when you lose the satellite input may cause problems, but you would have to try the upgrade to find out if that is the case, I expect.

Alternatively, it sounds as though Diff Lab could also build you a new 4.44:1 diff, which may be a cheaper option, even when including freight charges from Australia, as I can't see a specialist online that has the same capabilities as them in handling BMW diffs and is based in North America.

[XutvJet]

The 230 has a lower final drive than the 235/240 because the gearing of the transmission itself is longer. That's largely why it has a 3.91 final drive vs the 3.08 final drive in the 235/240 cars

An increased final drive will improve torque to the wheels and make the car feel more responsive, but there is a balancing act between too much gear and not enough. Also, don't forget that these are torquey turbo motors with lots of low end torque so they are not remotely as dependent on gearing. If you add a tune and downpipe, it becomes even less so as the motor doesn't need more torque multiplication when the motor itself is producing a lot of torque in the low and midrange.

I waivered on getting a deeper gear for my M235 but choose not too because I was going to add a tune and around another 70 ft/lbs of torque to the wheels at all points of the powerband.

In a perfect world, I feel like a 3.3 gear would be perfect for my M235 but it wasn't worth the price and I doubt much would change in terms of measureable acceleration. It would certainly feel quicker.

[sekhon]

I actually came up with this idea from stumbling upon those threads! I searched to see if someone had done this specifically with a 230i, and came up short... I would imagine that is because of the gearing already being short, not many people would want to go shorter. It does sit high in the RPMs on the highway and while I personally don't mind that, I am sure many others do!

Seems like I need to do a lot more research. This is likely something I start looking into after I take care of some basics, and do some easier mods first.

I appreciate the Diff Labs resource as well... and actually looking at ratio for an available shorter gear and considering the increased torque from it really solidifies that I will likely do this closer to the tail end of my modifications.

Overall though, I am very curious to understand more about the choices I can make for my car by changing the diff. Research, research, research.