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-   -   QTII/QDII Differentials (http://www.jeepgarage.org/f73/qtii-qdii-differentials-65995.html)

JRT1 09-27-2013 11:39 AM

QTII/QDII Differentials
 
Hey Guys,

I have been reading up on the QT2 and QD2 systems and there are a few things that I want to clarify.

On a 2014 with QT2, is the front axle a open diff and the rear a mechanical limited slip? I cannot find any mention on what is is, but I have to assume it is a mechanical LSD.

On QD2, I am sure the rear is an ELSD, which makes it be able to shift power to either wheel? And I believe I read since 2011 the front is now longer a ELSD, is it a open or a mechanical LSD? I assume it is an open diff so the computer can apply brakes to the spinning wheel, this would not be possible with a LSD...is this correct?

How much better is QD2 over QT2? I assume for the street with limited snow there is no rear need for QD other then having something extra to play with? :D

Thanks a bunch! :)

ColdCase 09-27-2013 12:06 PM

Re: QTII/QDII Differentials
 
There have been quite a few posts with discussion/descriptions. Both front and rear diffs are open unless you have the QD option (ELSD is what makes QTII into QD). Mechanical limited slips or lockers are not available on the WK2.

ELSD is only on the rear diff and is useful for reducing spin especially from a dead stop (like the SRT launch control) and for reducing wear and tear on brake pads off road, especially in mud. When you mash the throttle the traction control locks up the rear diff, it doesn't wait for wheel slip. I think its near lock when driving in rock mode.

You don't need QD but you will get where your going with much less drama. You also get more power to the ground with ELSD as you are not using brakes to turning power into heat to stop wheel spin (50% power to ground for BT, 100% for ELSD). Thus ELSD is much easier on the brakes (less brake wear)

All vehicles have the brake traction control on the front that applies brakes to stop a spinning wheel and direct the torque to the wheel with traction. Brake traction control is also used on the rear except when equipped with QD. The ELSD will direct torque to the wheel with traction (by locking the diff), no need for brake traction control. ELSD is much more efficient and has quicker response than brake traction control. Useful to you only if you need/want that.

JRT1 09-27-2013 12:29 PM

Re: QTII/QDII Differentials
 
ColdCase,

Thanks for the reply. I had no idea they are both open differential…that is horrible as I prefer a machine with an LSD in the rear.

So for QD if I were to take off quickly and say spin the tires without traction control on will both spin or just one?

I guess I have always felt it is better to propel a vehicle by driving both wheels in the rear.

f1anatic 09-27-2013 12:45 PM

Re: QTII/QDII Differentials
 
Quote:

Originally Posted by JRT1 (Post 900370)
ColdCase,

Thanks for the reply. I had no idea they are both open differential…that is horrible as I prefer a machine with an LSD in the rear.

So for QD if I were to take off quickly and say spin the tires without traction control on will both spin or just one?

I guess I have always felt it is better to propel a vehicle by driving both wheels in the rear.

You will be just fine.

Some of us (me) have taken their 45,000 dollar jewel and trashed in on trails and it did just fine. Coming from a Subaru with mechanical LSD differentials I had the same hesitation but I was pleasantly surprised to see the Jeep solution working beautifully. Not a perfect solution but it works great. Might have to change brake pads and discs more often if you do lots of off-roading but QT-II will be more than enough on a Grand Cherokee for the roughest terrain they are ever likely to see.

ColdCase 09-27-2013 02:52 PM

Re: QTII/QDII Differentials
 
Yeah I didn't mean to imply QTII with Jeeps traction control system is not a highly capable system, even QTI is pretty good if you don't drive places you need low range or decent control. QTII is capable enough that you don't "need" lockers, as many here can attest to. If you are rock climbing where you need lockers, the WK2 is the wrong vehicle to be using. Some will argue QD is much more effective in the snow/ice or at the race track.

When you mash a QD equipped vehicle's throttle, the diff is locked so both rear tires rotate at the same speed, depending on the traction situation they both spin or they both don't. In most modes, traction control will typically back off the throttle regardless when both rear wheels are spinning faster than the fronts.

lstowell 09-27-2013 05:06 PM

Re: QTII/QDII Differentials
 
Quote:

Originally Posted by JRT1 (Post 900370)
ColdCase,

Thanks for the reply. I had no idea they are both open differential…that is horrible as I prefer a machine with an LSD in the rear.

So for QD if I were to take off quickly and say spin the tires without traction control on will both spin or just one?

I guess I have always felt it is better to propel a vehicle by driving both wheels in the rear.

The hemi and i think the diesel have ELSD available on the rear.
Luckily they are also 4wd, as LSD in the rear on snow and a lot of applied power can point your vehicle straight ahead despite steering angle without the 4wd to help.

With the hemi on damp roads it does allow a nice 4 wheel chirp if you are easily amused.

JRT1 09-27-2013 09:52 PM

Re: QTII/QDII Differentials
 
Thanks for the info guys.

I am planning on a 13 or 14 with the hemi and was thinking about getting a Limited, but I think I want the QD2 now and they are hard to find with that option. I would have to go up to a Overland or a 13 Trailhawk, which I kind of like those Trailhawks alot so that may be the deal.

Northland 09-28-2013 06:29 AM

Quote:

Originally Posted by JRT1 (Post 900651)
Thanks for the info guys. I am planning on a 13 or 14 with the hemi and was thinking about getting a Limited, but I think I want the QD2 now and they are hard to find with that option. I would have to go up to a Overland or a 13 Trailhawk, which I kind of like those Trailhawks alot so that may be the deal.

It will be hard to find a '14 Limited with QDII on a dealer's lot as they'll prefer to stock the higher profit Overlands, but you can order the QDII with V8 on a Limited - I did.

whartung 09-28-2013 11:30 AM

Re: QTII/QDII Differentials
 
Quote:

Originally Posted by Northland (Post 900728)
It will be hard to find a '14 Limited with QDII on a dealer's lot as they'll prefer to stock the higher profit Overlands, but you can order the QDII with V8 on a Limited - I did.

Ditto. Ltd OR-II, RA-3, Dark Green, Frost interior -- there were pretty much NO Green JGCs, of any kind, near So Cal. Thankfully, there was at least one we could drive up to see, as the salesman warned us to go look at it, as it is a DARK Green.

What the dealers want to sell me, and what I want to buy are never congruent. Every JGC down here I think has a sun roof, and that's a $1000 I don't need to spend.

The wait can be frustrating, but we've ordered our last two vehicles, have been generally happy with the process. We tend to keep our vehicles a long time, so we may as well get what we want.

2014RedHemiGC 09-28-2013 04:51 PM

Re: QTII/QDII Differentials
 
Quote:

Originally Posted by Northland (Post 900728)
It will be hard to find a '14 Limited with QDII on a dealer's lot as they'll prefer to stock the higher profit Overlands, but you can order the QDII with V8 on a Limited - I did.

Had to order mine, too.

JRT1 09-28-2013 06:48 PM

Re: QTII/QDII Differentials
 
I don't think I am order because i am looking to strong arm a good deal! :D Can't do that if I am ordering. I's pretty ridiculous that all of the GCs don't come with the ELSD in the rear. Sucks!

mswlogo 09-28-2013 09:54 PM

Re: QTII/QDII Differentials
 
Quote:

Originally Posted by JRT1 (Post 901027)
I don't think I am order because i am looking to strong arm a good deal! :D Can't do that if I am ordering. I's pretty ridiculous that all of the GCs don't come with the ELSD in the rear. Sucks!

I got exactly the same deal ordering as the best deals on the lots for 2014. 2013 may be an entirely different story, different vehicle too. I got exactly what I wanted and exactly what I didn't want and saved even more. Don't rule it out. I would have paid more for what was on the lot because they all had things I didn't want/need.

Only 2014 you'll get some crazy deal on is one nobody wants.

Ordered my last 4 SUV's (3 of them Jeeps) and was very happy and kept them a long time.


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