[IMS-340C]

I noticed BMW offers the M Performance LSD with 3.23 for FD also 3.15 normal diff.

Has anybody tried changing to a different final drive ratio ?

[SC_B5X]

I'm curious about this. Following.

[B58togo]

You'll need to do some coding, otherwise you'll get all sorts of drive train malfunctions.

[///Madgreek1]

Originally Posted by B58togo

You'll need to do some coding, otherwise you'll get all sorts of drive train malfunctions.

To my knowledge the m performance lsd is fully mechanical and requires no coding. Changing the gear ratio in the diff has nothing to do with the computer, it's physically the gear set within the diff that determines the rotation of the axles.

[eksigned]

I always thought with boosted cars you wanted a longer final gear? These cars, especially with new turbos, etc. top out so quickly, I'd want something with a longer final beat, not shorter. No?

[///Madgreek1]

Originally Posted by eksigned

I always thought with boosted cars you wanted a longer final gear? These cars, especially with new turbos, etc. top out so quickly, I'd want something with a longer final beat, not shorter. No?

Depends on the end goal, acceleration off the line or top speed

[Nugget]

The manual could do with shorter gearing.
3rd goes to nearly 170kmh and 4th 230kmh.

[IMS-340C]

Coding is the easiest part since it's an OEM product the dealer should do it in little time with the installation.

Problem is it's very expensive where I live, anybody know where I can find a good deal on this one ?

Originally Posted by B58togo

You'll need to do some coding, otherwise you'll get all sorts of drive train malfunctions.

[kern417]

Originally Posted by ///Madgreek1

To my knowledge the m performance lsd is fully mechanical and requires no coding. Changing the gear ratio in the diff has nothing to do with the computer, it's physically the gear set within the diff that determines the rotation of the axles.

Originally Posted by IMS-340MP

Coding is the easiest part since it's an OEM product the dealer should do it in little time with the installation.

Problem is it's very expensive where I live, anybody know where I can find a good deal on this one ?

Definitely not. This was a practice back in my volkswagen days and it never got solved. Things like cruise control got disabled because the car can see a difference between the engine speed and wheel speed that doesn't match. The same reason why we can get drivetrain malfunctions when hooking up to a dyno.

The different ratios are offered for different options that came from the factory. You're supposed to buy the LSD that has the same F/D as your OEM diff. The dealer doesn't have an option to program the wrong diff to match your car.

Originally Posted by Nugget

The manual could do with shorter gearing.
3rd goes to nearly 170kmh and 4th 230kmh.

Unfortunately the manual already has the shorter gearing of the two.

[Ifellapart]

Originally Posted by kern417

Definitely not. This was a practice back in my volkswagen days and it never got solved. Things like cruise control got disabled because the car can see a difference between the engine speed and wheel speed that doesn't match. The same reason why we can get drivetrain malfunctions when hooking up to a dyno.

The different ratios are offered for different options that came from the factory. You're supposed to buy the LSD that has the same F/D as your OEM diff. The dealer doesn't have an option to program the wrong diff to match your car.



Unfortunately the manual already has the shorter gearing of the two.

If this is an M Performance upgrade from BMW, why wouldn't they code the car for it to work properly? There is absolutely no way BMW would ever drop the ball like that. Now if you installed it yourself, sure, I can see it messing some stuff up.

[kern417]

Originally Posted by Ifellapart

If this is an M Performance upgrade from BMW, why wouldn't they code the car for it to work properly?

because:

Originally Posted by kern417

The different ratios are offered for different options that came from the factory. You're supposed to buy the LSD that has the same F/D as your OEM diff.

If your car came with the 2.81 diff, buy the 2.81 LSD Differential
If your car came with the 3.23 diff, buy the 3.23 LSD Differential
You can't buy the wrong diff and ask them to make it work. If anything it would be more likely that someone on the consumer side would find an exploit to make it work. Not the OEM.

[jackstrath]

Originally Posted by kern417

because:



If your car came with the 2.81 diff, buy the 2.81 LSD Differential
If your car came with the 3.23 diff, buy the 3.23 LSD Differential
You can't buy the wrong diff and ask them to make it work. If anything it would be more likely that someone on the consumer side would find an exploit to make it work. Not the OEM.

Are people that naive that they think your average bmw dealer enjoy you messing with your car

I remember the carry on i had with a dealer when i coded my mirrors to fold in on long hold of the lock button.... they went and reprogrammed the module as they thought there was something up with the car

[IMS-340C]

I agree but we never heard of an Automatic transmission 340i/440i coming from the factory with the 3.23 Diff.

Originally Posted by kern417

because:



If your car came with the 2.81 diff, buy the 2.81 LSD Differential
If your car came with the 3.23 diff, buy the 3.23 LSD Differential
You can't buy the wrong diff and ask them to make it work. If anything it would be more likely that someone on the consumer side would find an exploit to make it work. Not the OEM.

[kern417]

Originally Posted by IMS-340MP

I agree but we never heard of an Automatic transmission 340i/440i coming from the factory with the 3.23 Diff.

Maybe I should clarify on what I mean by "option." I don't mean it like the ford mustang where you can order the car with varying gearsets. BMW picked a specific ratio for each combination of engine/transmission/drivetrain. So whatever diff was associated with your car's combination is what you need to order. They created a bolt-in LSD for whatever combination you have, whether it's 4 cyl/6cyl, manual/automatic, etc. That's why in your screenshot it says that the 2.81 is for automatic, and 3.23 is for others (manual). There was also a 3.15 option, i believe for awd models? But they don't make an LSD for x-drive cars.

[B58togo]

Originally Posted by ///Madgreek1

To my knowledge the m performance lsd is fully mechanical and requires no coding. Changing the gear ratio in the diff has nothing to do with the computer, it's physically the gear set within the diff that determines the rotation of the axles.

Not so at all. The M235i and M240i have slightly different ratios, hence different part numbers for the M Performance LSD's for the respective cars. My LSD was originally purchased by a gentleman with an M235i. He installed it and got drive train malfunctions, so he pulled it and bought the correct one. No more codes. The TCU is fully expecting to see a certain RPM at a certain speed in a certain gear and when it doesn't see what it needs to see, it throws malfunctions.

I'm not complaining. I bought an M Performance LSD with less than 100 miles on it for $1300.

[///Madgreek1]

Originally Posted by B58togo

Not so at all. The M235i and M240i have slightly different ratios, hence different part numbers for the M Performance LSD's for the respective cars. My LSD was originally purchased by a gentleman with an M235i. He installed it and got drive train malfunctions, so he pulled it and bought the correct one. No more codes. The TCU is fully expecting to see a certain RPM at a certain speed in a certain gear and when it doesn't see what it needs to see, it throws malfunctions.

I'm not complaining. I bought an M Performance LSD with less than 100 miles on it for $1300.

I suppose I didn't clarify. When installing the correctly geared differential there is no coding necessary, as the differential being a mechanical part is not coded. If you were to install the wrong part, you would recieve a drivetrain malfunction because of the feedback from other sensors that rely on wheel speed. That being said, a dealer is not going to re-code other systems and sensors to make an incorrect part work so really it's a moot point. I am curious how you would go about resolving the issues if you installed a custom geared quaife though, as I would assume you would have the same issue...

[jackstrath]

Originally Posted by ///Madgreek1

I suppose I didn't clarify. When installing the correctly geared differential there is no coding necessary, as the differential being a mechanical part is not coded. If you were to install the wrong part, you would recieve a drivetrain malfunction because of the feedback from other sensors that rely on wheel speed. That being said, a dealer is not going to re-code other systems and sensors to make an incorrect part work so really it's a moot point. I am curious how you would go about resolving the issues if you installed a custom geared quaife though, as I would assume you would have the same issue...

What do you mean? You are aware that the crown wheel from the standard differential is transferred over to the quaife. If your installing a custom geared quaife (as in a completely made to order part) your cars probable so heavily modified on on standalone ECU so it really doesn't matter at that point.

[///Madgreek1]

Originally Posted by jackstrath

What do you mean? You are aware that the crown wheel from the standard differential is transferred over to the quaife. If your installing a custom geared quaife (as in a completely made to order part) your cars probable so heavily modified on on standalone ECU so it really doesn't matter at that point.

I mean I was curious... isn't that what I said? I've not ever taken a car to that extreme, so i didnt know how that would be resolved lol

Anyways that was a bit off subject for the thread, the OP was asking about M performance diffs, not quaife custom so I'll save that for another time. To my original point though, if you install the correctly geared diff, there is no coding as part.of the process, that's all I was getting at. A diff is a mechanical part and as such does not need to be coded.

[gfa3]

Maybe everyone here knows this already but when I tried to order the M-performance LSD on my 340i xdrive I was told you can't install that on an xdrive car. Just throwing that out there.

[IMS-340C]

Anybody changed a rear differential ? is it an easy process ?

[RumDomRum]

I just did the diff swap today.

I have a 2019 440i Coupe MANUAL. It came with a 3.23 rear differential and an 0.845 6th gear.
I also own a 2019 440i Gran Coupe xDrive with the Auto. The auto came with 2.81 rear diff and a 0.634 8th gear.

At 90mph with the GC Auto my RPM is 1950. With the manual at only 80mph it was running 3100 RPM. I don't remember what it is at 90, but I think it was around 4k. I HATE the difference between the two because honestly, I liked getting almost 40mpg in the auto and hated getting only 29mpg in the manual.

So I purchased the M-Performance LSD diff in 2.81 (PN: 33108659989) and put it in the manual 440i.

Verdict: It's great.

Now at 80mph I'm at 2500rpm. It's never going to be as good as the auto since top gear is such a different ratio, but I'm enjoying every gear more. Now, if I lose grip on a hard accel, both rear tires go and the car doesn't do the side to side shimmy that is sometimes terrifying. The car is much more predictable and feels better planted.

The swap was straight forward and everything fit. All you need is a 50mm wrench (I purchased one from Harbor Freight) and normal BMW fitment tools (couple torx, 10, 13, 16 and 18mm).

Only issue I have discovered: RevMatch is now non-functional. I'm guessing I need to find some way to tell the DME the ratio is different. No fault codes, no lights, no drivetrain malfunction indicators, nothing. Speedo is still correct, as well.

[mike082802]

great to know and thanks for being the guinea pig. in the n54 world guys were doing this all the time, the mt was 3.08 and the auto was 3.46 and it was a direct swap, there was no such thing as rev matching back then. the mt diff carried a premium price. i am curious what 2nd, 3rd, and 4th are at redline.