4WD - Explaining the 3 Systems - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WK2 Grand Cherokee Forum > 4WD - Explaining the 3 Systems

Nitro Gear Packages Now Available at Rockridge 4wdJEEP Gear Change Packages From ROCKRIDGE 4WD. We Are DIFFThe ULTIMATE "Selectable" Locker System! Brough

Reply
Unread 10-26-2014, 01:44 PM   #16
Bent8
Registered User
2011 WK 
 
Join Date: Sep 2014
Location: Delta, B.C.
Posts: 9
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?

Bent8 is offline   Reply With Quote Quick reply to this message
Unread 10-26-2014, 05:14 PM   #17
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 4,765
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.
__________________
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline   Reply With Quote Quick reply to this message
Unread 10-26-2014, 05:53 PM   #18
Bent8
Registered User
2011 WK 
 
Join Date: Sep 2014
Location: Delta, B.C.
Posts: 9
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
Bent8 is offline   Reply With Quote Quick reply to this message
Unread 01-14-2015, 11:22 PM   #19
perpster
Registered User
2015 WK 
 
Join Date: Dec 2014
Posts: 161
Very helpful thread. Jeep does not do a good job explaining the 3 systems.
perpster is offline   Reply With Quote Quick reply to this message
Unread 01-15-2015, 05:26 PM   #20
rockspyder
Registered User
1997 TJ Wrangler 
 
Join Date: Feb 2002
Location: southern Maryland, western shore
Posts: 245
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...
rockspyder is offline   Reply With Quote Quick reply to this message
Unread 01-15-2015, 05:42 PM   #21
2014RedHemiGC
Registered User
2014 WK 
 
Join Date: Jul 2013
Location: Beech Mountain, NC
Posts: 157
I thought Sport mode only affected the transmission shifting and had nothing to do with the differentials.
__________________
2014 Deep Cherry Red GC 4X4 V8 QDII
2012 Crystal Red Cadillac CTS-V Coupe
2011 Crystal Red Chevy Corvette Z06/Z07
2014RedHemiGC is offline   Reply With Quote Quick reply to this message
Unread 01-15-2015, 08:53 PM   #22
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 4,765
Quote:
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.
__________________
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline   Reply With Quote Quick reply to this message
Unread 01-15-2015, 08:57 PM   #23
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 4,765
Quote:
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.
__________________
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline   Reply With Quote Quick reply to this message
Unread 02-18-2015, 09:07 PM   #24
Ampt
Registered User
2015 WK 
 
Join Date: Feb 2015
Location: Milwaukee, Wisconsin
Posts: 19
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...
Ampt is offline   Reply With Quote Quick reply to this message
Unread 02-18-2015, 09:19 PM   #25
loveracing1988
Registered User
 
Join Date: Jan 2013
Posts: 822
Quote:
Originally Posted by Ampt View Post
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.
loveracing1988 is offline   Reply With Quote Quick reply to this message
Unread 02-18-2015, 11:23 PM   #26
ColdCase
My Reality Check Bounced
 
ColdCase's Avatar
2011 WK 
 
Join Date: Sep 2009
Location: New England
Posts: 4,765
Yes 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.
__________________
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
ColdCase is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.