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Unread 09-10-2006, 08:27 AM   #1
jthomaslambert
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Liberty Selec-Trac vs Commander Quadra-Trac II

Hi Folks--can anyone tell me what the difference would be between my Liberty's Select-Trac (in 4-wheel part-time) vs. my Commander's Quadra-Trac II? I'm in Canada so my biggest "need" reason for the 4x4 is winter driving (heh, as opposed to the obvious "fun" reason).

Also, for winter driving, how much more effective would the Quadra-Drive II be over the Quadra-Trac II (I know--buyer's remorse question right)?

Thanks!
J.

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Unread 09-10-2006, 01:25 PM   #2
goose1
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from my understanding, the Libby's Selectrak allows you to have a part time 4WD system that can also function as a full time system. but you have to select the full time position for it to work. plus, i think it only sets up the drive train at a 48/52 split.
QTII is a selectless full time 4WD system. it is always on and ready to go. i think it's default is a 48/52 split front and rear, but it can change in less than a second to any number of configurations. so basically you have 4WD all of the time whether you need it or not, but don't have the situation where you might want to have it, but can't make that decision until it's a little too late. (suddenly finding yourself in a really bad rain storm and having to fumble for a lever to put the Jeep in 4WDFT.) QTII just does it for you.

QDII is a bit more advanced and has front and rear locking diffs. this allows the vehicle to not only transfer power to any axle, but also any wheel. if you aren't going to be "wheeling" severely, you probably would never need this. but it is a really great 4WD system.
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Unread 09-13-2006, 07:58 AM   #3
jthomaslambert
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Excellent information--thanks!
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Unread 09-13-2006, 10:06 AM   #4
ArloGuthroJeep
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The QTII transfercase (NP247) also defaults to RWD until slippage is detected which causes the PC (Progressive Coupler) to transfer power to the front drive train.

When Selec-Trac is in Part-Time mode the front & rear drive shafts are locked going the same speed. This is bad for any type of pavement since it doesn't allow the front & rear drive shafts to rotate at different speeds. When Selec-Trac is in Full-Time is essentially keeps the TC as an open-differential. Allowing the front and rear drive shafts to turn at different speeds and thus be driven on any surface.
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Unread 09-13-2006, 11:12 AM   #5
jthomaslambert
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So what would be more effective--Selec-Trac Fulltime or QTII? Almost sounds like Selec-Trac Fulltime would be faster/more responsive to something like winter driving because if it does slip, it's already in 4wd? Or is QTII so fast to react that it's moot?
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Unread 09-13-2006, 01:14 PM   #6
ArloGuthroJeep
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QTII is better in snow then Selec-Trac(ST) in Full-Time(FT). This is because with ST in FT it acts as an open differential, meaning equal torque is applied to each axle. If the rear axle is on ice that means it requires very little torque to get it spinning. As a result the same amount of torque is applied to the front wheels. Meaning the front barely gets any power.

In QTII it'll transfer up to 48% of the torque to the front as soon as the rear starts to spin.

Selec-Trac is nice when you want to be in Part-Time and have the front and rear drive shafts locked. That provides the best acceleration on snow/ice/gravel but at the expense of not being able to drive on pavement like that. Selec-Trac also has more aftermarket support then Quadra-Trac.

Both transfer cases are good. and QTII detects slippage (mechanically) so quick it doesn't matter that it defaults to 2wd.
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Unread 09-13-2006, 01:40 PM   #7
goose1
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arlo, you say that it will transfer up to 48% to the front axle. it was my understanding that it could transfer 100% to the front axle if it was needed. the 48% was the standard setting but could adjust 100% either way if the smart computer so determined. is that correct?
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Unread 09-13-2006, 02:56 PM   #8
ArloGuthroJeep
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Fine....make me go look it up

http://www.wkjeeps.com/
http://www.xkjeeps.com/
For those that don't know about those sites...

http://www.wkjeeps.com/wk_4x4.htm#QTII - It doesn't mention the percentage so I am not sure any more. It is a different transfer case then what the WJ's use (the 247 which is 48% I am pretty sure) so it very well could be 100% to the front I don't know for sure anymore

Edit: Just read further down and it defaults to 48/52 and from there can transfer 100% to the front...My bad

For those that haven't seen Quadra-Drive II offroad it works amazing. Even though what the diffs have aren't really lockers at all, it is just as capable as a Jeep with lockers
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Unread 09-13-2006, 03:16 PM   #9
jthomaslambert
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Ahh...it's all becoming clear now ;-) So then the major difference between QTII and QDII is that QTII can transfer power to a specific axle while QDII can transfer power to a specific wheel?

EDIT: Doh! Just read your link so now I'm confused again. It appears that QTII does vary the torque at the individual wheels just as QDII does. They use the same transfer case but the key difference is the ELSD functionality of the QDII system. Now, you'll have to help me out here. It sounds to me like QDII and it's ELSD would really be like driving a Selec-Trac in PART-time mode with the great advantage of having an automatic switch from locked to slip so that you don't see the stutter you'd have if you tried to drive a PT Selec-Trac on a dry surface. Kind of a "best of both worlds" if you will.

If that's correct, then QDII is predominately intended for off-road application?
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Unread 09-13-2006, 04:19 PM   #10
goose1
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OK. let me try my hand at this. and you will really have to excuse me because i have read a couple of different tries at this.

QTII is a FT4WD that has a 48/52 default setting. it will transfer torque to which ever axle has the most traction. it also uses its ESP to act like a LSD by braking the wheel that is spinning due to lose of traction thereby routing torque to the wheel with the most traction. i have also been told that the even though it has a default of 48/52 it mostly rides as a 2WD vehicle because the front doesn't always need that most. that is really not confirmed, but the Jeep website shows it that way and the stealership explained it that way to me.

now. QDII is exactly the same set up in every way except that it can transfer power to one wheel (a true limited slip diff). it can also, by detecting slip, lock up the axle like a true Diff lock. over on the JU forum there is a guy having a bit of trouble with that due to a lift and 285/75s he installed. nothing really serious, but because of the ESP system overall he is getting more feedback due to the mods done on his WK.

in my opinion, this is a great system. it is entirely hands free and the Jeep does all the work for you. unlike the Liberty Selectrac in which you will have to tell it if you want 2WD, 4WDFT, 4HI or 4LO. even though it offers more options, i really think this QTII or QDII are the better options. kind of like what is used on the Rangie and i think we can all agree that is a very capable off road vehicle.

i hope that helped. i know i might be more confused now.
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Unread 09-26-2009, 06:20 PM   #11
oldmac1
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I have had Select Trac, QT11 andf QD11 and all are really great systems. I love the Select Trac but the issue that was pointed out regarding shifting is correct. The driver needs to make decisions regarding if he wants the 4wd engaged or not. Small point and nothing wrong with that but the ease of QT11 and QD11 lets the Jeep decide what it needs and you just drive normally. Great for when the roads are patchy in spots and that removes all doubt about when to shift in my thinking. Good luck.
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Unread 09-27-2009, 12:35 AM   #12
colinzj
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A lot of the confusion is Jeep's fault: They reuse the same names over and over and over for vastly different technologies.

While the WJ and the WK both have "Quadra-Trac II," they're totally different systems that behave in opposing ways. They're only similar from a marketing standpoint—the driver doesn't need to do anything.

Quadra-Trac has been used for something like half a dozen different transfer cases now (some of which didn't even have low range) and we're only on the "2" version.

Quote:
Originally Posted by goose1 View Post
That is really not confirmed, but the Jeep website shows it that way and the stealership explained it that way to me.
The "how the 4WD systems work" on the Jeep site is awful. It's been consistently wrong since they introduced it years ago. If you pay careful attention, you'll notice the audio for both QTI and QTII is right while the illustration is for the WJ. The QDII demo is what's right for all of the WK t-cases if you ignore the bit about the ELSDs (and low range if you're talking QTI).
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Unread 09-27-2009, 10:38 AM   #13
LouC
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My 07 WK HEMI has Quadradrive II so I will see how it does this winter...my old 98 ZJ 4.0 has selectrac and it worked great in the winter...even in full time you almost always had more than enough traction...the only time the open diff in the transfer case issue was apparent was when the rear wheels were on ice and the fronts on snow or pavement...yes then the rears could just spin...I always used winter tires and my ZJ is unstoppable in the snow....the nice thing about the old school NV 242/Selectrac is that it's all mechanical...no electronics....so you have to know how to use it and it's limitations...but I feel for a an on/off road Jeep it's better than some of the newer systems because you can lock it in 4-high...my old 98 just needs a good limted slip in the rear (like a True-trac) to be as good off road as Quadradrive II....
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Unread 10-30-2009, 05:17 AM   #14
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This is a decent demo to watch... (click below)

Jeep - 4x4 Basics - How Jeep 4x4 Systems Work - Quadra-Trac II - 4WD SUVs

On the left you can see how all the other drive systems perform also.

Quote:
Originally Posted by jthomaslambert View Post
Hi Folks--can anyone tell me what the difference would be between my Liberty's Select-Trac (in 4-wheel part-time) vs. my Commander's Quadra-Trac II? I'm in Canada so my biggest "need" reason for the 4x4 is winter driving (heh, as opposed to the obvious "fun" reason).

Also, for winter driving, how much more effective would the Quadra-Drive II be over the Quadra-Trac II (I know--buyer's remorse question right)?

Thanks!
J.
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