[E90convert]

Originally Posted by F87source

Yeah the rear diff is pretty "dumb", in that it has 3 modes (open, LSD, and fully locked) and these modes are activated based on what the car wants. Calibration is likely just how the car activates the 3 diff modes based on yaw and wheel speeds.

Unfortunately I have no idea if I have access to those tables, I'll have to check, but I'm currently still over seas so I'm still extemely busy with work. I still need to check those temp tables for you but that's also back logged behind the things I'm obligated to do first.

With PWM driving the actuator position, BMW can provide a different actuator position for whatever scenario the controller decides. The calibration tables will tell us how incremental it is. I'd agree with your assumptions in the previous post that it the PWM probably is 5% increments which would give 20 different actuator positions possible based on the input parameters.

[E90convert]

It's actually detailed quite well here.

http://f80.bimmerpost.com/forums/att...5&d=1406475520

[F87source]

Originally Posted by E90convert

With PWM driving the actuator position, BMW can provide a different actuator position for whatever scenario the controller decides. The calibration tables will tell us how incremental it is. I'd agree with your assumptions in the previous post that it the PWM probably is 5% increments which would give 20 different actuator positions possible based on the input parameters.

It could be but I don't know for sure yet, the drive line masters video (or whatever their channel name was) seems to think there are only 3 positions where there is a substantial impact on diff performance.

Originally Posted by E90convert

It's actually detailed quite well here.

http://f80.bimmerpost.com/forums/att...5&d=1406475520

I can't open this for some reason.

[E90convert]

Originally Posted by F87source

It could be but I don't know for sure yet, the drive line masters video (or whatever their channel name was) seems to think there are only 3 positions where there is a substantial impact on diff performance.


I can't open this for some reason.

PDF page 63 states specifically it is position controlled motor with a PWM signal. It has all the right ingredients for a highly controllable, variable locking diff. Neat too, that it automatically recalibrates the lock-up position after 1000 km or 100 kJ which "corresponds to a lap of the Nurburgring."

Interestingly the tech document for the F80/82 specifies a fluid change every third oil change, whereas the F87 tech document specifies every 5th oil change. Yet, official BMWUSA maintenance guides are every 5th oil change.

[vrooooom]

I'm still trying to get my head around the spider gears and its rotation to allow diff speeds on each wheel. Engineering!

are there a set of clutch packs for each L&R wheel? or just one as shown on that video.

[E90convert]

Originally Posted by vrooooom

I'm still trying to get my head around the spider gears and its rotation to allow diff speeds on each wheel. Engineering!

are there a set of clutch packs for each L&R wheel? or just one as shown on that video.

No just one clutch pack. A clutch pack on either side is more like the Audi Sport Diff or focus RS diff or MK8 Golf R. Those offer more will slip control at the expense of cost and weight.

[Westersund]

So both the gearbox and rear axle survived 3870 km to Germany and back, including about 400 km around the Nürburgring. Just wanted to let you guys know in case you want to step out of that cozy BMW dealership bubble and try something that works great for a lot less money.

[F87source]

Originally Posted by Westersund

So both the gearbox and rear axle survived 3870 km to Germany and back, including about 400 km around the Nürburgring. Just wanted to let you guys know in case you want to step out of that cozy BMW dealership bubble and try something that works great for a lot less money.

Good to know!

For me atleast, MSP/A from bmw is still cheaper than Castrol syntrax.

[doughboy]

How much for a diff oil change?

I found spec of 1.2L, but MPS/A oil is £35/L in 1L bottles.

[E90convert]

Yeah it’s a little more than 1L which is kinda annoying. Just changed it and it took about 1.1-1.2L. I think in the benchmarking study we did at work at was around 1140ml, I can double check the reports. Not sure if that was dry fill or wetted fill though.

Edit: I checked the report it is 1120mL to bottom of fill plug at 0 degrees pinion angle. With the pinion tipped up slightly in the installed position (4 degrees maybe?), it might be slightly less than this.

[F87source]

Originally Posted by doughboy

How much for a diff oil change?

I found spec of 1.2L, but MPS/A oil is £35/L in 1L bottles.

Diff is exactly 1L (as per ISTA), as soon as exactly 1L is filled it will start to dribble out of the fill port.

I also measured it when I drained it, and it was exactly 1L (filled up the original MSP/a bottle)

6mt is 1.3L.

[doughboy]

Thanks, 6mt 1.3 seems better than the 6.5L i found on one forum 🤣

[F87source]

Originally Posted by doughboy

Thanks, 6mt 1.3 seems better than the 6.5L i found on one forum 🤣

6.5L?! That's as much as the engine! That actually might be for the dct though.

I can screen shot the ISTA docs for you, so you know I'm not making stuff up. Just don't let me forget, I'll be home in a few hours.

[Track/S]

Originally Posted by F87source

6.5L?! That's as much as the engine! That actually might be for the dct though.

I can screen shot the ISTA docs for you, so you know I'm not making stuff up. Just don't let me forget, I'll be home in a few hours.

if one day you run out of ISTA you will not know how to tighten a screw 😂

[F87source]

Originally Posted by Track/S

if one day you run out of ISTA you will not know how to tighten a screw ��

So you're implying you don't follow bmw's prescribed fill volumes and torque specs? That's confidence inspiring for any potential customers coming to your shop.

[doughboy]

Originally Posted by F87source

6.5L?! That's as much as the engine! That actually might be for the dct though.

I can screen shot the ISTA docs for you, so you know I'm not making stuff up. Just don't let me forget, I'll be home in a few hours.

I've got ISTA, used it for years, didn't know it had fluid volumes or torque settings? Where's that?

I just use it for fault diagnostics and wiring diagrams

[TheHaze]

I just wrapped up the rear diff fluid flush right now and can confirm the capacity was exactly 1L as others above have said. Torque value for drain/fill plugs are 45 Nm per ISTA.

[F87source]

Originally Posted by doughboy

I've got ISTA, used it for years, didn't know it had fluid volumes or torque settings? Where's that?

I just use it for fault diagnostics and wiring diagrams

It's part of the vehicle management section. I'll share some screen shots and that's should be enough ro you to get a hang of it.

[F87source]

Originally Posted by doughboy

I've got ISTA, used it for years, didn't know it had fluid volumes or torque settings? Where's that?

I just use it for fault diagnostics and wiring diagrams

So image 1:




You will notice under the vehicle management tab and then repair/maintenance tab and then product structure, you will get a bunch of categories related to the car. If you click on rear axle-> rear-wheel drive, guide -> rear axle final drive

you will get information on the diff.

Next I will click on REP oil change in the rear axle final drive.






Image 2:




This is the rear diff oil change guide, it will tell you how to change the diff as per BMW AG, so the info contained here is as per BMW and the correct way to change the oil on the diff - no one else's opinion has any weight compared to this.


So you will notice the tightening torque is 33 11 5AZ (the 5AZ part is critical so memorize it), if you click on that this page will pop up:




Image 3:




If you look at the table and 5AZ, you will notice screw plug with o-ring (this is the diff drain and fill bolt). The next thing you will notice that it is mandated that you replace both screw plugs - likely because the o-rings will be deformed and unable to seal properly after 1 use. Next you will notice that the torque spec is 45 NM.




If we refer back to Image 2 you will notice there is a technical data hyperlink for filing capacity. If you click on that you will get this:




Image 4:




This table will tell you how much oil the diff takes, and for both a brand new diff and for a diff oil change you require exactly 1 liter, no more no less.


If you have your car on a level surface (I measured my garage with a level before doing this), you will notice that after exactly 1L of diff oil has been pumped in there will be a very slow thin dribble of oil from the fill plug, and thus the diff indeed is full at 1L. I also measured 1L of used oil drained out as well, so there is that.



Hope this helped!

[F87source]

Originally Posted by Track/S

if one day you run out of ISTA you will not know how to tighten a screw ��

Prime exhibit of what happens when you think you know everything (and it's worse because you own a shop - where customers trust you with their car and expect you to do things as PER BMW's spec, so I hope you follow ISTA word for word on customer cars):

From this thread: https://f87.bimmerpost.com/forums/sh....php?t=1938793





As per ISTA, BMW stipulates that you are not to drive without the stiffening plate in place. I suspect this is due to the possibility of the sub frame damage due to torsional strains, in conjunction with debris damaging the oil pan. But since the M4 GTS with the stiffening plate cover in place still requires the stiffening plate, I suspect it must be due to structural rigidity requirements.




So what does Track/S do with his ifinite "wisdom", he deletes the stiffening plate and replaces it with a thin carbon cover that not only is rigid enough to provide additional structural rigidity for the car, but is also only attached by the flimsy trim screws that are secured to the plastic underbody panel - and note, these screws are NOT meant to handle any significant loads....














This is why I will NEVER ever trust a shop to do work on my car, because you never know if they will do things by the book (torque specs, filling capacities, or critical BMW guide lines), or think they know everything and just end up doing sketchy things like this. Lets just hope you read ISTA carefully for your customers.



Like I said in the original thread, the idea of creating a carbon stiffening plate cover is ingenious, it would be a really great item to sell as an aero device to help clean flow over the stuffening plate. But deleting the stiffeing plate and replacing it with this is a bad idea.

[Track/S]

You don't know what that cover is used for so don't say things you have no idea.

[doughboy]

Originally Posted by F87source

Hope this helped!

Just a bit! Many thanks for taking the time to post all that.

I recently upgraded ISTA but now it won't connect to the car, spending too much of my life trying to find out why...