Excelsior7

This forum is getting inappropriate.

On a constructive note, so for someone who has a 2011 S4 with Sport Rear Diff, the car will always have at least 3 powered wheels, correct? I don't put much trust in Brake-actuated differential tech.

I'm also glad to hear that the E-diff is separate from the ESP and Traction controls. the 335i can't turn off TC without also turning off the E-diff, which in a RWD car, makes getting moving difficult in the snow.


With my car on the way, it's so wonderful to keep learning about these little hidden features.

helix139

No, you won't always have 3 wheels with power. You will have at least 1 on each axle with power, though, and as long as a rear wheel has traction you will have traction.

Excelsior7

Okay, help me with this, then.

If the center diff can lock up, that means that both driveshafts will get power, meaning at least one front wheel and one rear wheel will be powered.

And if the rear diff can also lock, that means that both rear output shafts will get power, so both rear wheels and one front wheel will be powered.

What am I missing? Is the sport rear diff -not- capable of locking? I had heard that it was.
Or maybe that was in the context that it could direct power away from a wheel without traction.

helix139

The sport diff has the capability to vector 100% of power to either rear wheel, not necessarily a 50/50 split, and the open diff in the front will send 100% of power to any wheel that has no traction. The center diff guarantees the front and rear will both receive power. Thus (assuming a 2011 crown gear) you could be sending 80% to a rear wheel with traction and 20% to a front wheel with no traction. If no wheels have traction, then yes, 3 of them will receive power.

Gear Junky

You are talking about the BMW promo videos where they show a Q5 having problems getting drive when 1 axle is completely without traction, like on rollers. LOL

It's an unrealistic situation to be in, but you are correct that in such a scenario the car would go nowhere.

Excelsior7

Ok, thank you, I was correct in the intent of my post, but wrong in the details.


Subaru uses a similar display, though aimed at Honda/Toyota

IncredibleMulk71

So am I one of the few people that didn't know you need to hold down the button to turn off both ESP and ASP?

Does turning both off increase your straight line speed?

CJ_S4

Noticed earlier on in this thread that the 2011's were updated with the crown gear diff. Is that really the case? I heard the 2013's got an updated version of quattro as well. What is different?

helix139

It was never completely settled, and probably won't be unless someone opens up the case on theirs.

CJ_S4

Got it. I'll report back next time I pop mine open to refill the bearing fluid.