[johnung]

Originally Posted by weehe126

He was pointing out that the N55 and B58 LSDs are not the same or interchangeable and this is the B58 section.

Yeah, I got that. I was pointing out that if you read New Posts within this application, they all appear to be from the overall generic 3/4 Series forum. It doesn’t indicate if a particular new post was originally posted in a sub forum. Don’t assume that I went into the B58 sub forum and decided to comment. Never went into the B58 sub forum. The post initially appeared like a generic F-30 post to me.

[johnung]

Originally Posted by YASBBYM3

Why not post it in the M3/M4 sections as well. As much relevance there as in the B58 subgroup 🤦‍♂️

M3/M4 is not part of the F30 forum, and again I didn’t post in the B58 subgroup. Never even opened the B58 subgroup.

[kern417]

Anyway, someone tell me why I should by the lsd i bought for my manual 440i (3.23) and install it on my auto 340i (2.81)

I understand that manual swap is easy and just disables rev matching, but putting a manual LSD on an auto sounds like a more complicated task. Normally I wouldn't shy away from potentially weeks of development and testing but I don't have that sort of time this go around

I'm tempted to just sell it and by the auto version for an easier time all around.

[SuperLomi]

Originally Posted by kern417

Anyway, someone tell me why I should by the lsd i bought for my manual 440i (3.23) and install it on my auto 340i (2.81)

I understand that manual swap is easy and just disables rev matching, but putting a manual LSD on an auto sounds like a more complicated task. Normally I wouldn't shy away from potentially weeks of development and testing but I don't have that sort of time this go around

I'm tempted to just sell it and by the auto version for an easier time all around.

I can’t comment on the physical differences, but people tried this previously on the N55 car’s, and found the car was throwing drivetrain errors or having other issues because of the different final drive ratio. And there’s no known way to adjust what the car is expecting. It sounded like this was only an issue for car’s with the auto. Changing final drive in the manual seemed to be ok from what I recall.

I can’t imagine it’s different for the LCI cars.

[kern417]

Originally Posted by SuperLomi

I can’t comment on the physical differences, but people tried this previously on the N55 car’s, and found the car was throwing drivetrain errors or having other issues because of the different final drive ratio. And there’s no known way to adjust what the car is expecting. It sounded like this was only an issue for car’s with the auto. Changing final drive in the manual seemed to be ok from what I recall.

I can’t imagine it’s different for the LCI cars.

I found the way to adjust it in ISTA

From my research everything bolts up. But it requires adjustments to the DME and TCU for it to work without errors.

I think I'm going to try it

[IMS-340C]

Would be great if you can compare Dragy 100-200 or 60-130 for both diffs.

Originally Posted by kern417

I found the way to adjust it in ISTA

From my research everything bolts up. But it requires adjustments to the DME and TCU for it to work without errors.

I think I'm going to try it

[SuperLomi]

Originally Posted by kern417

I found the way to adjust it in ISTA

From my research everything bolts up. But it requires adjustments to the DME and TCU for it to work without errors.

I think I'm going to try it

Cool, make sure to document everything and share your process and results!

[SpencerC_6MT]

Thought I should add my experience in here, since it's relevant. I swapped the stock 3.08 open diff in my M240i to a Diffsonline 3.46 Wavetrac, and have since put over 10k miles on it.

The car does not like it. Every time I've started this car for the past year, it's in limp mode. Eventually the drivetrain malfunction warning stopped popping up, but the car always limits itself to 100nm of torque. After digging through codes, I discovered that it's throwing codes for clutch damage. In other words, the car is seeing higher RPM than expected in-gear, seeing that I'm off the clutch pedal, and assuming the clutch is cooked. The trick I've discovered is to accelerate up to about 15mph, let off the gas for about 3 seconds and let it decelerate in 2nd. The car seems to "learn" that the higher RPM isn't due to clutch failure, and drives completely normally until the next time the ignition is turned off.

However, this seems to be the only issue. If the e-LSD is wreaking havoc in the background, I haven't noticed. Cruise control is just fine, the speedometer is unchanged. I don't know about auto rev-match, since I did some Bimmercode fuckery a long time ago to permanently disable it, but I assume that would go out the window.

[SpencerC_6MT]

Originally Posted by IMS-340C

Did you notice more acceleration as a result of the increased torque/hp to the wheels ?

Yes, it felt noticably faster. The axle ratio is 12.3% shorter, so the same engine output equals 12.3% more power to the wheels. If you go off the rated 335hp number, it's roughly equivalent to the engine now producing 376hp. Of course, the downsides are ever-present. You reach redline sooner in each gear, especially noticable above 3rd, and turn about 300 RPM higher at highway speed in 6th.

[McBobby Jr]

I can’t comment on the 6-speed, but I do feel like the 8-speed paired with a higher hp output could benefit from a shorter final drive. I feel the OEM final drive ratio for the 8-speed does suit the stock turbo well.

[kern417]

Originally Posted by SpencerC_6MT

Thought I should add my experience in here, since it's relevant. I swapped the stock 3.08 open diff in my M240i to a Diffsonline 3.46 Wavetrac, and have since put over 10k miles on it.

The car does not like it. Every time I've started this car for the past year, it's in limp mode. Eventually the drivetrain malfunction warning stopped popping up, but the car always limits itself to 100nm of torque. After digging through codes, I discovered that it's throwing codes for clutch damage. In other words, the car is seeing higher RPM than expected in-gear, seeing that I'm off the clutch pedal, and assuming the clutch is cooked. The trick I've discovered is to accelerate up to about 15mph, let off the gas for about 3 seconds and let it decelerate in 2nd. The car seems to "learn" that the higher RPM isn't due to clutch failure, and drives completely normally until the next time the ignition is turned off.

However, this seems to be the only issue. If the e-LSD is wreaking havoc in the background, I haven't noticed. Cruise control is just fine, the speedometer is unchanged. I don't know about auto rev-match, since I did some Bimmercode fuckery a long time ago to permanently disable it, but I assume that would go out the window.

Try using ISTA to teach the new ratio

Originally Posted by McBobby Jr

I can’t comment on the 6-speed, but I do feel like the 8-speed paired with a higher hp output could benefit from a shorter final drive. I feel the OEM final drive ratio for the 8-speed does suit the stock turbo well.

I was thinking the opposite. Shorter for stock turbo.

[McBobby Jr]

Originally Posted by kern417

I was thinking the opposite. Shorter for stock turbo.

I used the wrong terminology, what I meant to say was a lower gear ratio not shorter. I think for stock turbo, perhaps a shorter gear would be better but I think the stock ratio is good. But I feel like the shorter gear ratio would be the opposite of beneficial with a increased power output especially with a big turbo.

[SpencerC_6MT]

Originally Posted by McBobby Jr

I used the wrong terminology, what I meant to say was a lower gear ratio not shorter. I think for stock turbo, perhaps a shorter gear would be better but I think the stock ratio is good. But I feel like the shorter gear ratio would be the opposite of beneficial with a increased power output especially with a big turbo.

A shorter ratio for auto cars doesn't seem very beneficial to me, just because the amount of gears allow for such a wide range of ratios while not having huge jumps between gears. 7th gear in 8HP cars is roughly equivalent to my 6th gear, while their 5:1 is vastly shorter than my 4.11:1. So the auto has more down-low torque, smaller jumps between ratios in the mid-range, and more overdrive up top.

By contrast, the shorter ratio in my car comes with more benefits (and compromise). When stock, 1st topped out at 40mph, 2nd at 70, 3rd at 110, 4th at 150. The 1-4 shifts cause a huge drop in RPM, but the 4-6 are very close together. changing 3rd gear from topping out at 110mph to 95mph made driving more enjoyable, purely because I could wind out 3rd in an everyday onramp pull. I can even top out 4th (125 vs 150mph) without being on a dark highway at 1:00a. Of course, I turn 3300 revs at 80mph on the highway now. If only BMW had followed in Porsche/Chevy's footsteps and given us a 7th gear...

[McBobby Jr]

Originally Posted by SpencerC_6MT

A shorter ratio for auto cars doesn't seem very beneficial to me, just because the amount of gears allow for such a wide range of ratios while not having huge jumps between gears. 7th gear in 8HP cars is roughly equivalent to my 6th gear, while their 5:1 is vastly shorter than my 4.11:1. So the auto has more down-low torque, smaller jumps between ratios in the mid-range, and more overdrive up top.

By contrast, the shorter ratio in my car comes with more benefits (and compromise). When stock, 1st topped out at 40mph, 2nd at 70, 3rd at 110, 4th at 150. The 1-4 shifts cause a huge drop in RPM, but the 4-6 are very close together. changing 3rd gear from topping out at 110mph to 95mph made driving more enjoyable, purely because I could wind out 3rd in an everyday onramp pull. I can even top out 4th (125 vs 150mph) without being on a dark highway at 1:00a. Of course, I turn 3300 revs at 80mph on the highway now. If only BMW had followed in Porsche/Chevy's footsteps and given us a 7th gear...

I agree, a lower gear ratio makes more sense for the 8-speed auto than a higher gear ratio. For the 6-speed manual, that’s a different case but I suppose it’s all preference at the end of the day. I definitely look forward to a lower gear ratio when I get a limited-slip differential. A 7th gear for you manual guys would’ve made those highway trips more enjoyable lol.

[G.Newt]

Originally Posted by SpencerC_6MT

A shorter ratio for auto cars doesn't seem very beneficial to me, just because the amount of gears allow for such a wide range of ratios while not having huge jumps between gears. 7th gear in 8HP cars is roughly equivalent to my 6th gear, while their 5:1 is vastly shorter than my 4.11:1. So the auto has more down-low torque, smaller jumps between ratios in the mid-range, and more overdrive up top.

By contrast, the shorter ratio in my car comes with more benefits (and compromise). When stock, 1st topped out at 40mph, 2nd at 70, 3rd at 110, 4th at 150. The 1-4 shifts cause a huge drop in RPM, but the 4-6 are very close together. changing 3rd gear from topping out at 110mph to 95mph made driving more enjoyable, purely because I could wind out 3rd in an everyday onramp pull. I can even top out 4th (125 vs 150mph) without being on a dark highway at 1:00a. Of course, I turn 3300 revs at 80mph on the highway now. If only BMW had followed in Porsche/Chevy's footsteps and given us a 7th gear...

I've grown to appreciate the taller gears in my Blackwing vs my 340ix. Yeah it doesn't feel as twitchy/accelerate as fast, but it leaves me room to grow into the gears once I tune it. Being able to cruise at 85mph at 2600-2700rpm is much nicer than the 3k rpm I was at before. I'm typically 1 gear lower than I would be, or I wait a bit more mph before I shift. Also, it forces me to downshift a gear or 2 constantly if I want to pass. No complaints since the Tremec TR-6060 is world's better than whatever ZF 6-speed BMW uses. Makes me enjoy rowing the gears.

Basically, BMW could've geared the manual better, even with just 6 speeds, but I get it.

[kern417]

Usually the optimal gearing will have you staying at or below your 1:1 gear in whatever your preferred metric is. So in an Auto, you shouldn't have to shift past 6th in a quarter mile, 60-130, etc. The 8 speed can do 200mph lol. On a stock turbo I could see shorter gears giving you more acceleration without having to go into overdrive gears where the gains aren't worth it. Once you have a bigger turbo, then taller gears make sense for both traction and keeping the cars gearing in power.

[bradsm87]

Originally Posted by kern417

Try using ISTA to teach the new ratio

Where can I find this? I thought I had a pretty good look.

I changed diffs from 2.81 to 3.38 in my F25 X3 30d. I flashed the ECU and DDE with all known references to final drive ratio after comparing ROMs against other vehicles ROMs known to have a different diff ratio. I still get 2 faults from the EGS (Auto TCM), 420474 and 420611 for non-permissible deviation between vehicle speed and output shaft speed. I'll keep investigating and go over the differences between ROMs over the next few days.

[bradsm87]

Found it.

It works! 2.81 > 3.38 and no faults after the relearn

[kern417]

Originally Posted by bradsm87

Found it.

It works! 2.81 > 3.38 and no faults after the relearn

If you can show how you found it, that would be great.

I know you can drive the car, let it throw codes, then use those codes to find the functions. But I'm not sure how to find it natively.

[Dom147]

I'd love to hear updates on this. kern417 did you ever try the swap? I think it'd make for a great video.

[kern417]

Originally Posted by Dom147

I'd love to hear updates on this. kern417 did you ever try the swap? I think it'd make for a great video.

I had both diffs in the garage but abandoned the project because I had a track day coming up and was running out of time. i may try again in spring but it's on hold for now

[SpencerC_6MT]

Originally Posted by bradsm87

Found it.

It works! 2.81 > 3.38 and no faults after the relearn

I don't have ISTA, but I recently bought ProTool, which supposedly has most the same capability. Where did you find this under? I'm going to see if I can work it out to cure the "clutch slip" codes.