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Common to all Jeep models is the Selec-Terrain modes of the AWD system, here are the functions of Selec-Trac...



Standard:

Default mode for the BU Renegade will keep it FWD majority of the time. Standard mode will split torque depending on circumstance.

Sport:

Reduces the range of traction control and increases the limits of stability control. Will split torque 40/60 front/rear to provide a more RWD experience.

Snow:

System kicks off in second gear, optimally calibrates brake settings for slick surface. Snow mode automatically shuffles the system into full time AWD with a 60/40 front/rear split.

Mud/Sand:

Also kicks off in second gear, full time AWD with a slight rear bias power distibution.

Rock:

Only available on the BU Trailhawk, Rock mode is only selectable in low gear. It increase brake lock capacity and locks the diff.
 

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Auto Mode Indication?

Hi there,

Have been driving my new Jeep Renegade in a lot of snow and on icy roads. I have used the knob to select Snow mode but I mostly left it in Auto mode.
My question is if there is some way to see when it shifts from 2WD to 4WD?
I could feel it and hear it, I think. But I would prefer to see it on the display.

Br, Kent
 

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How can it be possible to send more than 50% of available torque to the rear wheels when, even if the AWD diff is fully locked, the rear wheels essentially get "locked" to the front wheels in terms of their driving force? In order to route more than 50% of available torque to the rear wheels, the fronts either have to be slipping or some sort of mechanical overdrive to the rear wheels would be needed (ala Audi's recent quattro systems found in the A4 and up).
 

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How can it be possible to send more than 50% of available torque to the rear wheels when, even if the AWD diff is fully locked, the rear wheels essentially get "locked" to the front wheels in terms of their driving force? In order to route more than 50% of available torque to the rear wheels, the fronts either have to be slipping or some sort of mechanical overdrive to the rear wheels would be needed (ala Audi's recent quattro systems found in the A4 and up).
I'm speculating a bit based on what has been said and from looking at the videos, but my best guess is that the awd set up is basically a multi plate wet clutch pack for the center diff, and an open diff up front and in back. (Ignoring the drive shaft disconnect implementation ) So to get 100% of the force to the rear, it'd lock the center diff and use the abs to lock the front wheels. I don't think the 100% to rear situation would ever happen on anything but loose surface at low speed swith slip. There are other ways to do it, so that isn't a definite answer.
 

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I'm speculating a bit based on what has been said and from looking at the videos, but my best guess is that the awd set up is basically a multi plate wet clutch pack for the center diff, and an open diff up front and in back. (Ignoring the drive shaft disconnect implementation ) So to get 100% of the force to the rear, it'd lock the center diff and use the abs to lock the front wheels. I don't think the 100% to rear situation would ever happen on anything but loose surface at low speed swith slip. There are other ways to do it, so that isn't a definite answer.

Exactly. It isn't possible to overdrive the rear wheels relative to the front unless the front wheels are slipping and the system is applying the front brakes to prevent the front wheels from spinning, and the rear wheels have traction. That is, the Renegade's system (like every FWD-based AWD system, to the best of my knowledge) is a 50x50 torque split, at best, when all wheels have traction.



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Exactly. It isn't possible to overdrive the rear wheels relative to the front unless the front wheels are slipping and the system is applying the front brakes to prevent the front wheels from spinning, and the rear wheels have traction. That is, the Renegade's system (like every FWD-based AWD system, to the best of my knowledge) is a 50x50 torque split, at best, when all wheels have traction.



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I do not believe that is the case. At least according to subaru, my legacy GT is something like 60 or 65% rear biased. The caveat there is I don't know if you regard the way they lay out their transmission as being actually a FWD design. THe year I purchased it, that was only the case with the turbo and 5 spd automatic as it required the computer controlled clutch pack. From teh explanations I saw at the time, it basically used the clutch pack to generate that slip.

But in general, by definition, any design requires slip someplace to have anything other than 25% of the power going to each wheel as to have less or more means that wheel will wind up spinning at a different rate of speed. They usually only bring the breakdown of distribution up in two situations. First like with my legacy GT, and with things like the GTR, which is to describe it's default intended behavior under hard acceleration that has not been compormised by traction (i.e. if behaves like FWD or RWD until wheels slip), or to describe the limitaitons on the AWD system before it starts dragging or overspinning a wheel. For example my eclipse GTX. The viscous center diff permitted a maximum 45/55 or 55/45 split before it jsust spun all foru wheels regardless. Or at least tried until your transmission or transfer case decided it was going to introduce unlimited slip.
 

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I do not believe that is the case. At least according to subaru, my legacy GT is something like 60 or 65% rear biased. The caveat there is I don't know if you regard the way they lay out their transmission as being actually a FWD design. THe year I purchased it, that was only the case with the turbo and 5 spd automatic as it required the computer controlled clutch pack. From teh explanations I saw at the time, it basically used the clutch pack to generate that slip.

But in general, by definition, any design requires slip someplace to have anything other than 25% of the power going to each wheel as to have less or more means that wheel will wind up spinning at a different rate of speed. They usually only bring the breakdown of distribution up in two situations. First like with my legacy GT, and with things like the GTR, which is to describe it's default intended behavior under hard acceleration that has not been compormised by traction (i.e. if behaves like FWD or RWD until wheels slip), or to describe the limitaitons on the AWD system before it starts dragging or overspinning a wheel. For example my eclipse GTX. The viscous center diff permitted a maximum 45/55 or 55/45 split before it jsust spun all foru wheels regardless. Or at least tried until your transmission or transfer case decided it was going to introduce unlimited slip.
Modern Subarus uses a few types of AWD systems, but their most basic is a fully mechanical system that normally distributes torque 50/50 but can redirect torque to any one wheel or front/rear axle if one or more wheels are slipping. It can do so because it uses the brakes to stop a wheel/axle without traction from spinning (it uses open front and rear differentials). The more complicated AWD system found in Subaru's performance vehicles like the WRX and STi have both a mechanical link and a viscous coupling. By varying the viscous coupling, they can achieve a rear-biased torque distribution.

From an engineering standpoint, if you're not familiar with the concepts, it can be hard to understand torque distribution versus wheel speed. They are not one in the same. This video does a decent job of explaining. If you were to take the Torsen differential and apply it longitudinally, you'd have Audi's rear-biased quattro system (only the A4/A5/A6/A7/A8/Q5 and their performance variants use this type of AWD; the A3/Q3/TT use a Haldex FWD-based system similar to the Renegade's).

In order for the Renegade to have a rear-biased AWD system, it would need a coupling that engages the rear wheels and a longitudinal differential that allows for a front or rear torque bias. From what I've read of the Renegade's AWD system, it's a pretty typical system that basically varies the lockup of the coupling between the front and rear axles, with some manual control over it (i.e., the different user-selectable modes), and I think it may have the ability to proactively lock the coupling to help avoid wheelspin altogether (some FWD-based AWD systems have this ability, like some VW/Audi Haldex systems). At full lock, it drives the axles equally. At less than full lock, it favors the front.

I could be completely wrong with this, and the Renegade may have a more sophisticated system, but from what I've read, it's a pretty typical system for a FWD-based vehicle. The exception may be the Trailhawk model, though I think it's low-range is more a function of the transmission having an additional final drive rather than the AWD system being different.
 

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I just wanted to add that the rear-biased Audi systems actually use a crown gear setup to bias torque to the rear, but it's a similar concept to the longitudinal Torsen differential.
 

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I have heard multiple Jeep representatives say that the system can send 100% of the power to ONE wheel, if it's the only wheel with traction.

Am I misunderstanding something?
 

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I have heard multiple Jeep representatives say that the system can send 100% of the power to ONE wheel, if it's the only wheel with traction.

Am I misunderstanding something?
They have. It can. They also have said it has a multi plate wet clutch coupling at some point. Nobody has gone into detail on the design and software logic, which is where the answer is.
 
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