[tgmsocal]

OK, so I had to go to the tire place today to get the TPMS sensors switched out on the rims/tires I swapped over (prior BMW was 2013, wrong sensors). I picked this 2016 M235i 6MT up from the dealer used a little over a month ago and I continue to discover mods from the prior owner - they had no history on the car...

While the car was up in the air at the tire shop, I asked if I could go spin the rear tires to see if by some spot of fortune I have an LSD in there. Car was in neutral, e-brake off. Both wheels spun forward. Repeated multiple times, forward and reverse, always same direction.

Tried to get some pics of the diff (will add a post from my phone with them) but couldn't grab one of the top where the label is supposed to be. Tried to look the numbers in the pictures up via realOEM and Google to no avail - generic to both LSD and non-LSD.

I haven't driven a car with an LSD in a long time, the car feels good to me but haven't really had a chance to test it yet. Last test I know to try is to jack one wheel up and see how much force it takes to move the wheel that's in the air (should require a good amount of force with LSD).

TLDR; I need to know what kind of diff I have so I can buy the correct fluid for upcoming fluid changes. Installing FBO and changing oil/trans/diff fluids here shortly and the LSD and non-LSD use different fluids.

Thank you for any help you can provide, or tips you can add to what I've already found in searching. Not trying to rehash old ways of testing or anything like that.

[tgmsocal]

Photos attached

[ggggbmw]

The external casing of the LSD is identical to the standard diff. The only way to be sure is to get a view of the label on top of the diff. There are several threads on the forum debating about whether someone has an LSD or not, and viewing the label is the only sure way.

However, if you car was in neutral, and both wheels spun the same way, you probably got lucky.

[BimmerMRide]

I don't track my car, and had a few older cars with LSD...its quite impressive how well the eLSD does for spirited street driving....on a track would def. upgrade.

[tgmsocal]

FYI, as an update, I do have an LSD. Snapped a shot of the label when I did diff fluid change a few weeks ago. Not sure the photos I posted earlier are relevant at all.

[MAMSport]

Does the car need any coding if a LSD is added, to enable it to work properly? Or, must DSC need to be fully defeated?

[SpencerC_6MT]

My Wavetrac didn't need any coding as far as I know. I've driven it as-is about 3000 miles with no issues. The shortened gear ratio (3.08->3.46) does get the ECU confused sometimes, but I've learned how to work around that pretty quickly. Most people don't go for short gears anyways; as far as I can tell, I'm the only 6-speed B58 car with a 3.46:1 axle so far.

[Lingling]

Originally Posted by SpencerC_6MT

My Wavetrac didn't need any coding as far as I know. I've driven it as-is about 3000 miles with no issues. The shortened gear ratio (3.08->3.46) does get the ECU confused sometimes, but I've learned how to work around that pretty quickly. Most people don't go for short gears anyways; as far as I can tell, I'm the only 6-speed B58 car with a 3.46:1 axle so far.

Originally Posted by MAMSport

Does the car need any coding if a LSD is added, to enable it to work properly? Or, must DSC need to be fully defeated?

Add onto this thread as well. I just installed a Quiafe LSD about 500Mi ago I went from a 3.08—> 3.23. N55 6 speed. No issues so far. You can code DSC if you would like it’ll prevent the computers from interfering before the lsd has a chance. But I haven’t notice that too much in my experience.

[MAMSport]

Thank you both!

[designatedposter]

Originally Posted by SpencerC_6MT

My Wavetrac didn't need any coding as far as I know. I've driven it as-is about 3000 miles with no issues. The shortened gear ratio (3.08->3.46) does get the ECU confused sometimes, but I've learned how to work around that pretty quickly. Most people don't go for short gears anyways; as far as I can tell, I'm the only 6-speed B58 car with a 3.46:1 axle so far.

what kind of ECU confusion?

[SpencerC_6MT]

Originally Posted by designatedposter

what kind of ECU confusion?

The car starts in limp mode most of the time. You get power for a split second after every shift before it dies again. If you let it coast in-gear for a few seconds, that seems to convince the car that the clutch isn't slipping, and it drives completely fine until the next startup. I've talked to a couple people who have changed the ratio on their N55 cars and they don't get this issue. It seems that the B58 ECU is programmed to protect the clutch if it detects slip, and my car is interpreting the elevated RPM at a given speed as clutch slip.

[Zychrias]

Just for asking sake:

If the car was on a lift, in Park, no E-brake and the wheels turned together forward or backward. Would that make it not an LSD? What is the technical reason on why it would need to be in Neutral?

Assuming RWD only, not Xdrive.

Thank you!

[aerobod]

Originally Posted by Zychrias

Just for asking sake:

If the car was on a lift, in Park, no E-brake and the wheels turned together forward or backward. Would that make it not an LSD? What is the technical reason on why it would need to be in Neutral?

Assuming RWD only, not Xdrive.

Thank you!

The output shaft from the transmission has to be able to rotate freely, as opposed to being locked in position if in park. If it can’t rotate freely, then the rear wheels can’t be rotated in the same direction, only in the opposite direction to each other.

[ggggbmw]

Originally Posted by aerobod

The output shaft from the transmission has to be able to rotate freely, as opposed to being locked in position if in park. If it can’t rotate freely, then the rear wheels can’t be rotated in the same direction, only in the opposite direction to each other.

The 'rotate freely' part is key. After I got my LSD I was questioning the traditional wisdom of LSD's turning both wheels in same direction, because mine didn't. They turned opposite because my automatic transmission was in Park.

As soon as I put the transmission in Neutral, then the wheels DID turn in the same direction. This is complicated by the fact that it's hard to put the AT in neutral unless the car is running. (There is a mechanical way to do it by tightening a bypass bolt.)

You can see this in a poor video I did:

[ferraricare]

Just posted one in the classifieds if anyone's looking.