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Unread 10-26-2014, 12:44 PM   #16
Bent8
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Just so I'm clear, in QTII auto mode, the front and rear drive shafts are turning under control of a clutch pack which is controlled by a traction computer. The mode selector, under control of the traction computer governs the ratio of slippage in the transfer case front to rear when one of the tires breaks loose.
So if this were the case, in sport mode, the clutch pack would be adjusted to give more traction to the rear than the front possibly causing the rear tires to break away more easily.
Is this, in simple terms, about right?

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Unread 10-26-2014, 04:14 PM   #17
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Its perhaps simpler than that. The transfer case directly connects the transmission output to the rear axle, no clutch involved, there is no way to disconnect the rear axle. The clutch disks are alternately splined to the front and rear drive shafts and connects the front axle anywhere from 0% to 100% lock. When disengaged no (0%) power is supplied to the front axle, when engaged (100%) its like the common 4WD lock mode. Sport mode probably loosens the clutch pack more than normal mode and therefore makes it feel more like a RWD vehicle. So I guess running in sport mode would cause less clutch wear than normal mode.

Sport mode also adjusts a number of things including stability and traction control and transmission shift points. But yes, if you want to squeal the tires, sport mode is the best one to use.... although if you have a V6 dunno if that helps enough.

Note that the "capability to transfer 100% of power to one axle or the other" description can be misleading. In approximate terms, when there is zero rear axle traction, 100% of the engine power goes to the front axle. When there is zero front axle traction, 100% of the power goes to the rear axle. When all wheels have the same traction, its effectively a 50/50 power mix.
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Unread 10-26-2014, 04:53 PM   #18
Bent8
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I think I get it now. The fact that only the front dif is clutch driven is key to my understanding. Thanks for all of the great info!
Al
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Unread 01-14-2015, 10:22 PM   #19
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Very helpful thread. Jeep does not do a good job explaining the 3 systems.
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Unread 01-15-2015, 04:26 PM   #20
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Quote:
Originally Posted by ColdCase View Post
They will slip a bit as you go around turns and more if you drive with different size tires on each corner. These kinds of clutches have been used in transfer cases for decades and the only time they seem to be an issue is when they overheat during wildly spinning tire escapades typically in muddy or deep sand conditions. The have a long service life in typical street duty, 200,000 miles plus.
Quote:
Originally Posted by ColdCase View Post
Its perhaps simpler than that. The transfer case directly connects the transmission output to the rear axle, no clutch involved, there is no way to disconnect the rear axle. The clutch disks are alternately splined to the front and rear drive shafts and connects the front axle anywhere from 0% to 100% lock. When disengaged no (0%) power is supplied to the front axle, when engaged (100%) its like the common 4WD lock mode. Sport mode probably loosens the clutch pack more than normal mode and therefore makes it feel more like a RWD vehicle. So I guess running in sport mode would cause less clutch wear than normal mode.

Sport mode also adjusts a number of things including stability and traction control and transmission shift points. But yes, if you want to squeal the tires, sport mode is the best one to use.... although if you have a V6 dunno if that helps enough.

Note that the "capability to transfer 100% of power to one axle or the other" description can be misleading. In approximate terms, when there is zero rear axle traction, 100% of the engine power goes to the front axle. When there is zero front axle traction, 100% of the power goes to the rear axle. When all wheels have the same traction, its effectively a 50/50 power mix.
So in "Auto" mode, no slippage of the clutches unless there is a difference in front and rear wheel speeds. No slippage in "Low" because they are locked together. I still don't understand the "Sport" mode, though, I think. Transmission is "hard linked" to the rear through the xfer case, but "Sport" loosens the clutch-pack. So it CAN spin the rear (if it has enough power and/or low-enough traction), which might cause more wear on the clutches if it happens a lot (say driving down a muddy road in "Sport" all the time -- which would be foolish anyway). But otherwise, the front and rear wheel speeds should be the same, with looser clutch-pressure, so it should reduce the wear over time to the clutches of taking turns and corners (say lots of city driving -- which is going to wear out the vehicle quicker anyway, since I think that qualifies it for the severe-duty cycle of maintenance).

All that sound about right? Sorry for the long post, just wanted to make sure I understand, and it helps me to type through it...
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Unread 01-15-2015, 04:42 PM   #21
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I thought Sport mode only affected the transmission shifting and had nothing to do with the differentials.
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Unread 01-15-2015, 07:53 PM   #22
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Originally Posted by 2014RedHemiGC View Post
I thought Sport mode only affected the transmission shifting and had nothing to do with the differentials.
The traction control computer puts a little RWD bias in when in sport mode. It also has some affect on the yaw and stability control as well as the throttle response curve. Its more than simply adjusting the transmission shift points.
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Unread 01-15-2015, 07:57 PM   #23
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Originally Posted by rockspyder View Post
So in "Auto" mode, no slippage of the clutches unless there is a difference in front and rear wheel speeds. No slippage in "Low" because they are locked together. I still don't understand the "Sport" mode, though, I think. Transmission is "hard linked" to the rear through the xfer case, but "Sport" loosens the clutch-pack. So it CAN spin the rear (if it has enough power and/or low-enough traction), which might cause more wear on the clutches if it happens a lot (say driving down a muddy road in "Sport" all the time -- which would be foolish anyway). But otherwise, the front and rear wheel speeds should be the same, with looser clutch-pressure, so it should reduce the wear over time to the clutches of taking turns and corners (say lots of city driving -- which is going to wear out the vehicle quicker anyway, since I think that qualifies it for the severe-duty cycle of maintenance).

All that sound about right? Sorry for the long post, just wanted to make sure I understand, and it helps me to type through it...
I think that sounds about right... if I followed you right... its not clear if there is that much difference in clutch wear, however.
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Unread 02-18-2015, 08:07 PM   #24
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So is it possible to stick the rear differential from a QD2 onto a QTII? I'm assuming you would need to reflash with the correct program and probably run the extra wire to the back differential...
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Unread 02-18-2015, 08:19 PM   #25
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So is it possible to stick the rear differential from a QD2 onto a QTII? I'm assuming you would need to reflash with the correct program and probably run the extra wire to the back differential...
No, you need the controller to run it as well, and something to run that controller.
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Unread 02-18-2015, 10:23 PM   #26
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There is a QD control module and perhaps some wiring. Then you need to convince a dealer to add the QD option to the VIN and flash the update, perhaps similar to what they do to activate the trailer harness. Dunno if thats possible or if anyone ever tried it.
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Unread 08-15-2015, 04:13 PM   #27
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Here is an explanation of the 3 4WD systems that are used in the WK2. One is technically an AWD system, but we will not berate Jeep for calling it a 4x4 because the system uses magic sauce to make it the most capable AWD many have seen (more capable than many 4x4 systems on the market). The same components are used in all model years 2011-2014.

The order that follows is from least capable to the most capable. As always, feel free to comment or suggest improvements. This as a living guide that is changed and updated to integrate suggestions and to match the current WK2 capabilities.

The availability of one system over another varies from year to year. For example, some years Laredos can get QD, other years not. QD is only available on V8s and Diesels, however. wk2jeeps.com has a pretty good index of whats available year by year. It doesn't list those periods of times one option was restricted due to parts availability.

Quadra-Trac I

Features:

* No shift lever or driver interaction required.
* Full-time 4-wheel drive provides smooth operation and vehicle stability under all conditions because torque is constantly being transferred.
* Torque distribution provides traction to maintain forward motion under most conditions.
* The Brake Traction Control System (BTCS) works in tandem with full-time 4 wheel drive. BTCS provides resistance to any wheel that is slipping to allow additional torque transfer to wheels with traction.
* Robust design and improved sealing enhance reliability.
* No maintenance required.


Operation:

As mentioned above, this is a single speed transfer case that offers no locking center differential (part time 4wd setting usually known as 4 High on vehicles like the Wrangler). This allows the system to be used on the road in any conditions and traction quantities. In order to supply power to the wheels that do have traction, the ABS sensors determine when a wheel is slipping and apply the brakes to that side.

The differentials and transfer-case of the QTI are open. This means that the wheels are all allowed to spin at any speed regardless of the power being sent or the speed of the other wheels. If one wheel were to loose traction, all power would go to that wheel, and you would be stuck. With Brake Traction Control (BCT) (Jeep marketing likes to use the term Brake Locking Differentials (BLD) ), the ABS system detects when a wheel is spinning faster than the other wheels and applies the brake to that wheel. By applying the brake, it forces resistance to that wheel which allows the power to be sent to other wheels that have more traction.

These brake locking differentials do a great job of moving the power. Here is a perfect video of it in action on a patriot (different 4wd system, but it is still making the climb because of the BLD). Watch the tires of both the passenger and driver's sides to see when the brakes grab:

Because the differential is open, it is always changing the amount of torque that is being sent to the front and rear drive shafts. Some sources say that the split is 48/52 where 52% of the power is going to the rear to give the Jeep a sportier feel. One site claims that the split happens to be 50/50. According to the Jeeps website (http://www.jeep.com/en/4x4/how_syste...k/quadra_trac/) The system just transfers torque as necessary.

Edit: Updated by ColdCase Jan 15, 1015
Does the QT-I have a high and low range?
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Unread 08-15-2015, 04:57 PM   #28
Kev M
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Originally Posted by vjsimone View Post
Does the QT-I have a high and low range?
No
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