[Soravia]

Originally Posted by Impreza99

Taken from Subaru website:
"Available only on the WRX STI, this drivetrain is the most advanced and sophisticated of the four. With a 41/59 split, it leans more on a rear bias, which is ideal for a sport-focused drive feel. "

The earlier STI are even more rwd bias at 35/65 split. I am an owner of an 05 STI by the way.

Watched this video a while ago but if my memory is correct, the video describes the various awd system pretty well and touches on the previous generation.

Which tire wears out more often on your STI? My wife's CX-3 AWD wears out front more (rear diff fluid was like new on 30k).

My Miata rear tires wear out more and rear diff fluid was in need of change at 15k miles. granted, One made 140 HP and the other made 250 HP at crank

[Soravia]

Speed Master brand is having sale on LSD, has anyone tried them? About to pull the trigger but I have no idea of their build quality.

It says 27 spline for output. Not sure how many splines the LCI 328xi I have has.

https://speedmaster79.com/BMW-3-Seri...p-Differential

[carguy138]

I've owned a few of each and here are my thoughts. Also spent time on the track with the 335 and A4, as well as winter driving schools. All equipped with bridgestone blizzaks in the winter.

99 Subaru Outback: viscous center diff (felt very similar to Audi's torsen).
06 Audi A4: Quattro, torsen
11 335i xdrive: RWD with clutch controlled center transfer case.

The subaru and audi felt very similar on snow/gravel/dirt. Very confidence inspring when sideways and you felt like you could put the car exactly where you want it.

The bmw xdrive is herky/jerky and feels sketchy at higher speeds with moderate slip angles. Like everyone complains about the e-diff in the rear, the xdrive feels similar forward and aft.

In both below scenerios, figure 3rd or 4th gear with traction control fully off on a frozen lake or huge parking lot with snow tires.

When you tip into the throttle on the xdrive, the rear instantly kicks out. You counter steer and try hold it with a certain slip angle. Then you feel the clutch controlled transfer case kick in and start locking and unlocking quickly. Engine power is also reduced and the car trys to self correct. Momentum is killed and thats the end of it.

On the subaru and audi when you tip into the throttle it starts to understeer. Then with a bit more throttle and turn in, the rear comes out predictably. Now you can essentially keep the throttle at one position and control the slip angle with the steering wheel. Power isn't cut and you can accelerate through the powerslide. Just overall feels really confidence inspiring.

All systems are fine with decent tires on plowed roads to get you around town. But if you are doing winter driving schools, rally driving, etc., the torsen based audi and subaru are in a different league. With the audi and subaru I was confident enough to be able to pitch the car sideways on dirt/gravel roads in rural VT. With the xdrive, not at all.

I haven't driven any newer audi or subaru AWDs so I cannot comment on those. Maybe the best way to compare the systems is that the older subaru and audi AWD systems allow you to accelerate through a turn (while sideways) and the bmw xdrive tries to deaccelerate and retain control.

[Soravia]

I wonder what rear LSD in the xDrive with DTC OFF will do?
Will it put the car on AWD mode while not using brake based traction control?

[Impreza98]

Originally Posted by Soravia

Which tire wears out more often on your STI? My wife's CX-3 AWD wears out front more (rear diff fluid was like new on 30k).

That's a good question. I am unsure as I only dailyed the car for two years before regulating it to a summer car. I recently changed out my wheel/tire combo and didn't notice any perceived difference in wear (about 20k miles on Bridgestone re070).

In the Subaru community I don't hear uneven wear as being a problem as I do on here (rear tires wearing quicker).

[Soravia]

Originally Posted by Impreza99

That's a good question. I am unsure as I only dailyed the car for two years before regulating it to a summer car. I recently changed out my wheel/tire combo and didn't notice any perceived difference in wear (about 20k miles on Bridgestone re070).

In the Subaru community I don't hear uneven wear as being a problem as I do on here (rear tires wearing quicker).

If you haven't change out the diff fluid. xDrive front fluid was like near new even at 60k.

[Impreza98]

Originally Posted by Soravia

If you haven't change out the diff fluid. xDrive front fluid was like near new even at 60k.

I'm not following. Old differential fluid explains the lack of wear?

[Soravia]

If the fluid has been there a while and still clear it hasn't seen heat.
Torque puts on friction, friction makes heat. No torque -> clear fluid.

[E91WAG3N]

Originally Posted by carguy138

I've owned a few of each and here are my thoughts. Also spent time on the track with the 335 and A4, as well as winter driving schools. All equipped with bridgestone blizzaks in the winter.

99 Subaru Outback: viscous center diff (felt very similar to Audi's torsen).
06 Audi A4: Quattro, torsen
11 335i xdrive: RWD with clutch controlled center transfer case.

The subaru and audi felt very similar on snow/gravel/dirt. Very confidence inspring when sideways and you felt like you could put the car exactly where you want it.

The bmw xdrive is herky/jerky and feels sketchy at higher speeds with moderate slip angles. Like everyone complains about the e-diff in the rear, the xdrive feels similar forward and aft.

In both below scenerios, figure 3rd or 4th gear with traction control fully off on a frozen lake or huge parking lot with snow tires.

When you tip into the throttle on the xdrive, the rear instantly kicks out. You counter steer and try hold it with a certain slip angle. Then you feel the clutch controlled transfer case kick in and start locking and unlocking quickly. Engine power is also reduced and the car trys to self correct. Momentum is killed and thats the end of it.

On the subaru and audi when you tip into the throttle it starts to understeer. Then with a bit more throttle and turn in, the rear comes out predictably. Now you can essentially keep the throttle at one position and control the slip angle with the steering wheel. Power isn't cut and you can accelerate through the powerslide. Just overall feels really confidence inspiring.

All systems are fine with decent tires on plowed roads to get you around town. But if you are doing winter driving schools, rally driving, etc., the torsen based audi and subaru are in a different league. With the audi and subaru I was confident enough to be able to pitch the car sideways on dirt/gravel roads in rural VT. With the xdrive, not at all.

I haven't driven any newer audi or subaru AWDs so I cannot comment on those. Maybe the best way to compare the systems is that the older subaru and audi AWD systems allow you to accelerate through a turn (while sideways) and the bmw xdrive tries to deaccelerate and retain control.

Great insight. Appreciate the post! I’m looking at adding an xDrive car to my stable and haven’t driven any at the limit or on any surface other than asphalt/concrete.

[Soravia]

I drove the xDrive 328xi sedan in Colorado highway and streets during snow, frost, ice, blizzard with slush.

I had Bridgestone Blizzak WS-80 on them, as well as CX-3 AWD.
CX-3 had some lightness in the rear end on the same conditions doing 65 MPH on the highway. I can tell when CX-3 sends power to the rear. In mid corners during slippery conditions, it will want to come out in the rear like a RWD car, as the AWD sends power to the rear.
328xi was stable and planted (90k miles on the car, new dampers). I felt no difference in power output to the wheels. It just kept going.

[blown07]

I'm not sure putting an LSD into the weak front diff is a good idea. I don't mind the idea of power going to the wheel with the least traction during a first gear launch. With the LSD all the power has to go to both front wheels regardless of traction...yes a good thing if the diff can handle it...just a thought.

[Nick.B]

Originally Posted by carguy138

I've owned a few of each and here are my thoughts.
........
In both below scenerios, figure 3rd or 4th gear with traction control fully off on a frozen lake or huge parking lot with snow tires.

When you tip into the throttle on the xdrive, the rear instantly kicks out. You counter steer and try hold it with a certain slip angle. Then you feel the clutch controlled transfer case kick in and start locking and unlocking quickly. Engine power is also reduced and the car trys to self correct. Momentum is killed and thats the end of it.

On the subaru and audi when you tip into the throttle it starts to understeer. Then with a bit more throttle and turn in, the rear comes out predictably. Now you can essentially keep the throttle at one position and control the slip angle with the steering wheel. Power isn't cut and you can accelerate through the powerslide. Just overall feels really confidence inspiring.
.....
I haven't driven any newer audi or subaru AWDs so I cannot comment on those. Maybe the best way to compare the systems is that the older subaru and audi AWD systems allow you to accelerate through a turn (while sideways) and the bmw xdrive tries to deaccelerate and retain control.

Thanks for that. The driving experience of the x-drive sound terrible for someone who likes getting it sideways in the winter.

Your Outback almost certainly had an LSD in the back. Most did back then. A lot of the newers ones don't. Brand new 2019 WRX for example, open rear diff. Won't slide nicely through a corner, feels like FWD. Bolt in an LSD from an older Subaru, and it's just like you describe.

[nsjames]

I've never felt my xdrive clutches engage or disengage.

I have blizzaks on my junk right now.

it will get sideways. You just push the "I accept all responsibility for my actions" button on the dash marked DTC.

[Nick.B]

Originally Posted by nsjames

I've never felt my xdrive clutches engage or disengage.

I have blizzaks on my junk right now.

it will get sideways. You just push the "I accept all responsibility for my actions" button on the dash marked DTC.

Interesting. The post I quoted said the 'tests' were done with DTC fully off.

DTC button sees as much use as the start/stop button on my cars, lol.

Guess I should go drive one and make an opnion of my own.

[nsjames]

hold the button in longer for DSC off and it will let you slide sideways in a power slide.

it will not let you do a complete donut. Cuts the throttle about 3/4 the way through.

personally verified in my 08, YMMV depending on whatever.

the only time I've ever felt shudders from my transfercase was on hard surfaces in a tight turn, it had 110K miles on it and had never been serviced.
I changed it's fluid and did the reset and I've never felt it since. Currently at 155k. Two winters.

I don't know why they would feel the clutches engage and disengage, they're already engaged. The system splits 70/30 all the time.

there's currently 2" of slush on the roads and it's all going to freeze tonight.
I will do more testing, for science.

edit:
you know, that guy has a 335, so it's possible that with the aditional horsepower it simply overwhelms the ability of the case to cope, maybe even hits parameters BMW has programmed in to protect it from exploding.
I am a lowly 328.

[Nick.B]

Originally Posted by nsjames

hold the button in longer for DSC off and it will let you slide sideways in a power slide.
....
I am a lowly 328.

Well aware of the long push on the DTC.

Went to drive two 328s today. One wouldn't start, the other was tentatively sold and wasn't able to drive it. M-sport manual wagon.

[nsjames]

a m sport manual wagon would be a fantastic thing to own.

[Soravia]

Originally Posted by Nick.B

Thanks for that. The driving experience of the x-drive sound terrible for someone who likes getting it sideways in the winter.

Your Outback almost certainly had an LSD in the back. Most did back then. A lot of the newers ones don't. Brand new 2019 WRX for example, open rear diff. Won't slide nicely through a corner, feels like FWD. Bolt in an LSD from an older Subaru, and it's just like you describe.

ABS Brake DTC has been a bane of real LSD.
I want LSD but not sure if I can install one myself into a diff. Heard I have to use shims etc. No idea

[carguy138]

To give you guys something cool to watch and illustrate the point a bit better, here you go. This is the type of driving that I am talking about. The Audi torsen Quattro system feels almost identical to the older 50/50 torsen subaru AWD systems.

For reference on their channel they have an AWD mini cooper with a similar but reverse setup as BMW xdrive. Front powered with haladex clutch sending power to the rear. Similar to BMWs Xdrive that is RWD and uses a clutch to send power to the front. Point being it's an electronic reactionary system vs a mechanical proactive system. Reactionary systems are tough to predict when your messing around with left foot braking, weight transfer and stuff like that in slick conditions.



Not knocking BMW at all, it's just a different system designed more to get you home than anything else. I imagine after a few hours of sliding around you could overheat the transfer case oil in the xdrive and put it into limp mode.

For what it's worth I'm actually heading back to Team O'Neil Rally school this weekend with the 335 and will have plenty of time to play around with it again. Frankly the Xdrive annoyed me enough that I used Xdelete to turn it off and run it RWD. I've also coded off a lot of the throttle cut and braking systems.

With Blizzak WS90s and 100% RWD it does a great job in the snow and is pretty darn predictable. A rear mechanical LSD would be even better but not sure I want to dive into that.

If I were to do it all over again, I'd just get a RWD and run good snow tires in the winter.

[Soravia]

I got $150 quote to put in LSD into open diff. $150 for used diff, $750 for Torsen, plus $150 labor, and under $50 for seals and flange bolts, I'll be spending $1,000+ to put in a Torsen

[Nick.B]

Originally Posted by carguy138

To give you guys something cool to watch and illustrate the point a bit better, here you go. This is the type of driving that I am talking about.
...
Point being it's an electronic reactionary system vs a mechanical proactive system. Reactionary systems are tough to predict when your messing around with left foot braking, weight transfer and stuff like that in slick conditions.
...
I've also coded off a lot of the throttle cut and braking systems.
...
If I were to do it all over again, I'd just get a RWD and run good snow tires in the winter.

I understood your point from your earlier description, but the video was a fun few minutes.

As someone familiar with control systems, it's going to be a pretty big compromise when a control system is unaware of what the driver sees and is trying to do, and it's trying to keep the driver safe.

Where'd you find the info for coding out the torque cut and braking?

RWD with decent snow tires served me fine before we moved out here. Winters and road conditions here are much more severe. My house is on a hill. Small residential streets are never plowed. The road has three inches of ice, and a bit of packed snow on top. The RWD E90 with open diff and Conti snows will do it, but only barely some days. Thinking LSD and some winter rally tires for that car next year.

After adding the LSD in the back of the WRX, it drives great. Too bad it's got other.... issues... that shouldn't be effecting a 6 month old car with 10,000km on it.

[Blueeyesredpanda]

Originally Posted by paradoxical3

LSD works great on xdrive. I have about 10 days on my wavetrac and I am kicking myself I didn't do it earlier. You will need to code off the e-diff and other nannies, which you can see how to do on my blog: http://www.onelapx1.com/blog

Xdrive is really fantastic on track with a LSD; it's faster than RWD for sure. The cars I can keep up with are pretty ridiculous and I make up so much time coming out of turns at full throttle.

I tired to visit your website but its not connecting.