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Old 03-13-2012, 10:53 AM   #15
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The Air Suspension in the Grand Cherokee is a German designed and built, totally different kind of system from any I have ever seen. It is on all four corners of the vehicle, not just the rear. It levels the entire rig. It can lower the whole rig for ease of entry and exit. It can raise it for rock crawling (remember it is a Jeep). I think, but am not entirely sure it will even re level the car when stationary, that is I think I have seen it move when I was out of the rig. I have never heard any compressor running. When it raises from the lowest position used for ease in entry and exit, first the rear will come up, then the front, then the rear, then the front, all done in about half inch increments.

What I was hoping for was someone who had run into this on another Grand Cherokee, and had figured it out, or had seen some information from Jeep itself about how you were to hook up the (required by the manual) WD hitch system. Not all of the 2011 and 2012 GC's have the system, only the Overlands and up trim lines. But there have been thousands of them sold, so others must have run into the issue. A net search on my part has not run across any real information.

As I mentioned, I only have one 1000 mile trip towing on it so far. I had my 20' Argosy and even with essentially no tension on the spring bars of my hitch, it was exceptionally stable and rock solid as a tow vehicle. But I am still uncomfortable not knowing what is going on and what could happen in an emergency situation.

I thank everyone who has offered suggestions. Unfortunately this system is unlike any other and thus the ideas don't fit the specific thing that Jeep designed. If you do find any information anywhere about this Quadra Lift system, let me know.
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Old 03-13-2012, 11:20 AM   #16
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Although you will need to find the operating characteristics for this particular vehicle...maybe from Chrysler themselves, I think you will find the tweaking for proper WD will be very similar. I know nothing about the new Jeep system, but they are not the first to have air ride on all four corners (1958 Buick Roadmaster, among others...Citroen in the 1960s had it). What will be unique is the software and operating modes which you may encounter during normal towing situations.

I believe, you will find a compressor and level sensors though.
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Old 03-13-2012, 01:35 PM   #17
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Originally Posted by dznf0g View Post
Although you will need to find the operating characteristics for this particular vehicle...maybe from Chrysler themselves, I think you will find the tweaking for proper WD will be very similar. I know nothing about the new Jeep system, but they are not the first to have air ride on all four corners (1958 Buick Roadmaster, among others...Citroen in the 1960s had it). What will be unique is the software and operating modes which you may encounter during normal towing situations.

I believe, you will find a compressor and level sensors though.
I had one of those 58 Buick Roadmasters.

It had a fanastic ride, when the system was working.

In the morning, the car would typically have a 'lean: to one side or the other.

In all, 29 air bags were replaced before the cause of the problem was discovered.

Sort of unheard of, but the compressor had too much of a punch, everytime it cycled, which in turn caused a bag to ultimately fail.

The fix was to remove that system, or keep it and pay for all the bags.

That car needed a new bag, almost every week.

Oh well, we enjoyed the ride while it lasted.

Andy
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Old 03-13-2012, 02:28 PM   #18
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I had one of those 58 Buick Roadmasters.

It had a fanastic ride, when the system was working.

In the morning, the car would typically have a 'lean: to one side or the other.

In all, 29 air bags were replaced before the cause of the problem was discovered.

Sort of unheard of, but the compressor had too much of a punch, everytime it cycled, which in turn caused a bag to ultimately fail.

The fix was to remove that system, or keep it and pay for all the bags.

That car needed a new bag, almost every week.

Oh well, we enjoyed the ride while it lasted.

Andy
You, Sir, are exactly correct! Most of them were disconnected or removed. I found one in IMMACULATE condition for $3500 back in 1986. I had 2 small children and a third on the way, didn't have any extra$$$$. UGGGGG! Wouldn't that make a SWEEEEET vintage AS puller now!

TriviaÖÖ.That car had the most chrome plating of any car in automotive historyÖ..28 pounds!
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Old 03-13-2012, 07:00 PM   #19
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JEEP Grand Cherokee Quadra Lift

With the QL system I'd spend part of a day at the closest CAT Scale Locator (Lewiston or Missoula; want cross-reference quality values for any other US location in the future.)

I'd want to start a logbook of weights and adjustments, with accompanying photos.

The scale allows me to:

A] Play with WDH combinations. Since it'd be good to get all the numbers anyway (empty & loaded; TT & TV plus separate TW) one would be well ahead per all WDH questions.

1 - (Include published weight per DODGE)

2 - TV; empty but for driver, full fuel (and permanent additions)

3- TV; loaded for travel

4 - TT: empty but for full fresh water & propane (and permanent additions)

5 - TW

6 - TV & TT; hitched, but no WDH application

7 - TV & TT; hitched, with WDh application

IOW, there is not much of a way to find out how the thing works without scale weights.

We know -- according to current truck/SUV practice -- that we want the FA to return to the "laden, unhitched" value once the WDH is set; and the question remaining is how much is on the RA and the TT axle.

It might be that the old 1/3-1/3-1/3 "rule" works for this combo where FA, RA and TT wind up about the same.

Andy can clarify, I believe it was an FA/RA split of around 10% difference between those two axles once WDH adjusted, with the "extra" weight preferably on the RA (and the TT sort of falling where it will) as one is not ever perfectly going to get the three-way split.

B] The second item of great worth is tire load. Pressures are best set (towing or solo) according to load. And it can take a bit of experimenting to get those numbers. Since this is -- at present -- a bit of a weirdo, tire pressure is that much more important. It will be the "base" of how this rig feels short of the "best" WDH adjustments.

Ideal inflation pressure, according to tire engineer Barry Smith, will be found (paraphrased):

After steady state driving of 1.5-hrs; where the pressure rise is no more than about 5-psi after checking overnight cold temp pressure.


It is not max sidewall pressure, it is not max vehicle manufacturer number (although it could be either), and it is certainly not the solo value. One can come in quite high, and ideally one is spot on for best tire life, handling, braking and fuel economy. Too high is not good (and too low terrible).

See Barry's Tire Tech

I'm going to see if I can find anything on the GC. What's the vehicle spec? (A GC Turbodiesel is on my short list of "ideal" TV's).

.
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Old 03-13-2012, 07:33 PM   #20
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I see you've asked this question, here, and it is where I would start.


Also, from Down Under: http://caravanersforum.com/viewtopic.php?f=2&t=20882
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Old 03-13-2012, 10:49 PM   #21
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Rednax: Yes, I asked the question in the fall, and lost the thread, thanks for the help in re locating it, and the responses. Although they are for the Mercedes system, I think it is either similar or the same as the Jeep's as MB was still involved with Chrysler when this series of Jeep was being designed.

When I get back home in a couple of weeks I will do some serious work on the issue, weights and all, as well as trying to get some information from Jeep. I have an excellent small local dealer with a very good shop and service guy. They will be willing to talk with the zone reps I am sure, or have me down to show the problem. I had just thought that by this time, someone else may have had the issue (this is the second year of the Grand Cherokee with the Quadra Lift suspension), and I might shorten the process riding on others experiences.

Maybe I will wind up being the "expert" on the system, who knows. I just want to be totally safe and don't feel comfortable without my WD hitch doing some work.

I will be able to use the Idaho DOT State Scales when they are closed, as they are always left on. Unfortunately they are 100 miles from me.
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Old 03-14-2012, 10:15 AM   #22
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What I linked above was the extent of what I found. I would assume that the CW link from Australia would be worth following into what those guys found for Land Rover vehicles given care that their different percentage approach to WDH is clearly differentiated.

Yes, you may well become the point man for North America, ho! The weights posted and what hitching attempts show via different scale values would be useful to anyone else.

Is Lewiston (CAT Scale location at truckstop) really so far? An initial weigh is only $10, and all subsequent weighs that day only $1 or $2 each. Plus, being able to replicate them at any other location in the US would be great (not all scales are the same; CAT builds and adjusts theirs all the same).

Looking forward to what you come up with. Your own thread on the subject (with links to this and earlier/other posts) would be great.

.
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Old 03-14-2012, 12:51 PM   #23
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idroba and everyone else...if you get any good information on the Grand Cherokee please post it. I just bought a 2012 Grand Cherokee Overland to tow a new trailer and the vehicle keeps raising itself up and makes the trailer sit too high in the front. I have only towed it from the dealer to my home, and will make my first trip out this weekend, so I will see how it goes with the tension on the WD. I did a TON of research finding a mid-size SUV to tow with...and the Jeep was the best. It tows a lot and you can use a WD hitch - a rarity these days in the mid size SUV. I was certainly not expect these issues with the load leveling feature.
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Old 03-14-2012, 01:33 PM   #24
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Rednax and steveopt: I will be going home from my winter place in AZ in a couple of weeks, and then I can seriously work on this issue. I will start a new thread on the subject as this on has fragmented all over the place (my fault, but it was an accident).

Rednax: yes, unfortunately the scales I can get to and use are 100 miles west of my home, but that is the beauty and curse of living in the boondocks. I will use the Idaho DOT scales when they are closed but left on, that way I can take all the time necessary to measure and hook up and weigh at my own speed. It will also have a dead level location. I may have to get a new drop shank hitch stinger, as I am about as low as I can go on my current one. I have a new Dexter axle on the trailer, and new 16" wheels and tires, so I am pretty sure the trailer is good to go.

Steveopt: I feel your pain. As you may have seen in the manuals, Jeep requires a WD hitch for heavy tongue loads, but neglects to tell you how to use it in conjunction with the Quadra Lift system. I spent a couple of more hours yesterday on the Jeep forums and the only thing I found relevant to towing with the Quadra Lift was one photo of a GC and a car hauler trailer, which the poster said towed fine. But an inspection of the photo showed no WD hitch being used.

You may have to have a drop stinger for your hitch, as I suspect I am going to need to allow your initial hitch ball height on the trailer and on the Jeep be equal, unhitched, to start with. I suspect, but am not sure, that this might be a part of my own problem that will need to be resolved. Like you have found, my Jeep wants to raise the front of the trailer once it is hooked up. That then removes the tension from the spring bars of the WD hitch.

We will solve this, I am sure.
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Old 03-15-2012, 11:51 AM   #25
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idroba and everyone else...if you get any good information on the Grand Cherokee please post it. I just bought a 2012 Grand Cherokee Overland to tow a new trailer and the vehicle keeps raising itself up and makes the trailer sit too high in the front. I have only towed it from the dealer to my home, and will make my first trip out this weekend, so I will see how it goes with the tension on the WD. I did a TON of research finding a mid-size SUV to tow with...and the Jeep was the best. It tows a lot and you can use a WD hitch - a rarity these days in the mid size SUV. I was certainly not expect these issues with the load leveling feature.
Our local jeep dealer said that they thought that the load leveling could not be easily defeated / restored by the user (possibly with dealer reset via computer link)... something very essential with a WD hitch - as we are informed on this forum. We liked everything about the 2012 Grand C-Overland except for that undefeatable feature (none of the user settings would work)... bought a new truck instead (traded in wife's jeep wrangler - unsuited for towing AS to us due to short wheelbase). Hence my questions about spec'd hitch height ... we needed a new longer drop shank as well.
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Old 03-15-2012, 01:04 PM   #26
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A good addition to the "tow haul" ratings might be to include the hitch height for each of the vehicles.
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Old 03-15-2012, 02:24 PM   #27
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Our local jeep dealer said that they thought that the load leveling could not be easily defeated / restored by the user (possibly with dealer reset via computer link)... something very essential with a WD hitch - as we are informed on this forum. We liked everything about the 2012 Grand C-Overland except for that undefeatable feature (none of the user settings would work)... bought a new truck instead (traded in wife's jeep wrangler - unsuited for towing AS to us due to short wheelbase). Hence my questions about spec'd hitch height ... we needed a new longer drop shank as well.
mefly,

I think what you need to do is measure how high the tongue/ball height is with the TV and trailer hitched & loaded for camping, suspension activated no WD tension.

TV would then be level with the tongue high.

Use that measurement to get a drop stinger that will level the the trailer.

The question then becomes..how will the suspension react as the WD bars are tensioned. And more importantly how will it effect your CAT scale weights. You will still need to keep the str axel weights within the safe limits.

my 2 cents

Bob
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Old 03-15-2012, 04:38 PM   #28
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10-4; thank, Bob. I am now armed with a new more heavily "dropped" shank to put into the EQ hitch.
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