Rubicon Owners Question: Rainy Day Rear Axle Operation

[scgmc]

Given this scenario: You are sitting at a traffic light on a rainy day in the turn lane waiting to turn left. It appears clear at first and you start to turn, only to find an oncoming vehicle is actually bearing down on you, so you floor it....

Does the Rubicon’s open differential (when not locked via the dashboard switch) maintain constant forward momentum or just spin one-legged?
If it does continue with forward momentum...does it use BLD or some other traction control nanny to do it? Do you feel it happening?

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[Dogboyslim]

On snow, one wheel slips, then the stability control system kills the power and applies brakes to the free spinning wheel to get the other wheel to spin. It is very obviously happening.

 

[scgmc]

On snow, one wheel slips, then the stability control system kills the power and applies brakes to the free spinning wheel to get the other wheel to spin. It is very obviously happening.

Thanks for the reply. How about rain driving?

 

[roaniecowpony]

Thanks for the reply. How about rain driving?

The stability (traction function) control system doesnt know if the water is liquid or frozen or even if there is water or dry pavement. It measures wheel rotation on all the wheels.

 

[viper88]

Thanks for the reply. How about rain driving?

Same.

 

[scgmc]

10-4. Thanks y’all. That makes perfect sense. To the computer, lack of traction is just mismatched wheel speeds regardless of conditions.

I guess the part of it that worries me a bit is the “kills the power” part. If I’m trying to scoot out of the way of an oncoming car, the last thing I want is to be down on power.

 

[Neanderthalman]

10-4. Thanks y’all. That makes perfect sense. Lack of traction is just mismatched wheel speeds regardless of conditions.

I guess the part of it that worries me a bit is the “kills the power” part. If I’m trying to scoot out of the way of an oncoming car, the last thing I want is to be down on power.

While instinctively that makes sense, it's actually better that it kill the power. Did you learn "threshold braking" as part of driving? Think of it like "threshold acceleration". You want to accelerate as fast as possible without slipping. Because as soon as a wheel slips, all that "extra power" goes nowhere and actually slows down your acceleration by reducing friction between tires and road.

 

[scgmc]

Great explanation! I totally get it now. I’ve totally blown off the tires in my Formula and slightly backed off until they regain traction and then continued pouring it on to gain speed.

Other than cost and the red dash (not trying to hate, I just prefer the leather dash, which can be changed) the open diff (when not locked) was a Rubicon feature I wasn’t digging. It sounds like it is a non-issue during daily driving.

 

[Kpbergma]

I do a lot of driving in snow where I live. I have a Rubicon, but used to have a JK Sahara with limited slip in the back. The Rubicon is totally fine, but it was a bit of an adjustment. I felt the Sahara with limited slip handled accelerating in the snow better. That said, it had the gutless 3.8L v6 and 2.71 gears, so maybe it just didn’t have the torque to break the rear wheels loose as easily.

I was really torn between the Rubicon and a Sahara with limited slip with the Select Trac transfer case given how much snow we deal with. I think it’s an option really worth considering if you deal with a lot of low traction situations.

 

[Drytellsr]

10-4. Thanks y’all. That makes perfect sense. To the computer, lack of traction is just mismatched wheel speeds regardless of conditions.

I guess the part of it that worries me a bit is the “kills the power” part. If I’m trying to scoot out of the way of an oncoming car, the last thing I want is to be down on power.

You could always look both ways before you cross the street.

 

[roaniecowpony]

The traction control doesn't "kill" power, it moderates it, while the brake system modulates the wheel that is slipping which transfers torque to the other wheel. You end up with acceleration that is about as good as you'd get if you were a great driver (and on your game at that instant) with no traction/stability control and a limited slip, if the system is working right. If you're not a great driver all the time, it makes you better in most cases. In your hypothetical scenario, it would likely keep people out of the ditch that would have otherwise over powered the rear wheels and spun into the ditch.

 

[scgmc]

You could always look both ways before you cross the street.

Haha! I hear you smarty pants.
Guess you’ve never had the scenario where someone is sitting in the opposite (oncoming) left turn lane and then changes their mind and whips straight into the intersection. Or you just misjudged someone’s speed coming toward you.
Or a vehicle blends into the background....

 

[Sheepjeep]

the other thing to keep in mind in your scenario is the computer for traction control is looking at not only wheel slippage but also your steering input and a butt load of other sensors that feeding it data as far as how wild your driving is, and it will try to control braking to keep you upright and moving in the direction you want to go

 

[Drytellsr]

Haha! I hear you smarty pants.
Guess you’ve never had the scenario where someone is sitting in the opposite (oncoming) left turn lane and then changes their mind and whips straight into the intersection. Or you just misjudged someone’s speed coming toward you.
Or a vehicle blends into the background....

I try very hard not to be in those scenarios anymore, Its costs too much, I practice a little patience and caution in my older age. I used to take chances like you have described yourself in and tried to cut in front of on coming traffic. You can call it "Misjudging someones speed" but if we think about it we have all taken chances we should not have. You just seem like an aggressive driver with a heavy foot and very impatient.
Quote"
I’ve totally blown off the tires in my Formula and slightly backed off until they regain traction and then continued pouring it on to gain speed".
Situational awareness is best practice along with a little patience.

 

[scgmc]

I try very hard not to be in those scenarios anymore, Its costs too much, I practice a little patience and caution in my older age. I used to take chances like you have described yourself in and tried to cut in front of on comming traffic. You can call it "Misjudging someones speed" but if we think about it we have all taken chances we should not have. You just seem like an agressive driver with a heavy foot and very impatient. Quote"
I’ve totally blown off the tires in my Formula and slightly backed off until they regain traction and then continued pouring it on to gain speed". Situational awareness is best practice along with a little patience.

You have no idea what my driving style is, nor do I have to defend it to you. But I will.
I too, practice patience on the road.
If I don't have a comfortable window to cross traffic or pull out in front of others going the same direction, I wait. Riding a motorcycle on the street makes you acutely aware of this.
I was just asking when you NEED to get out of the way, and the conditions are slippery, will a Rubicon spin or go?
Again, you must be very lucky if you have NEVER found a need to quickly get out of the way.

BTW: It's pretty easy to spin tires on a manual transmission, high horsepower Formula.
You learn throttle modulation to save your tires, if nothing else.

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