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  #49  
Old 08-16-2012, 07:21 AM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

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Originally Posted by yoda42 View Post
The noise accrues on the black top, unless you are on the worst roads in the world or hitting a speed bump at 80 you will not top out this suspension, if you where the car would be bouncing all over the road, jack your car up and see how much wheel travel you have, this noise comes from minor road defects not major suspension travel, it is the sharp quick movements that cause the rattle/clunk
I have had my rear shocks replaced twice and the noise returns after about 300km on the new shocks
As an ex-mechanic I will state that it is not the shock coming to the end of its travel top or bottom making this noise, it is a problem with the internal valveing of the shock not the length
And yes I have had a very good look at the suspension, I have a 50mm lift that I installed my self
If this rattle/clunk was caused by the shock being to short it would be noticed more off road, I have had our GC off road many times and the noise does not occur when articulating the suspension off road, only on the black top with minor road imperfections where the suspension does not work through its full range of travel
Agreed. I have a knock - sounds like a loose short piece of wood bouncing around, but I only notice it on very small road imperfections. My subdivision road is one place. The road is quite level with no potholes - in fact they paved it just a few years ago. However it developed cracks and the cracks sunk in just a bit. You can barely feel them in the Jeep and even on my mountain bike they are pretty minimal. But on every single one I get a 'clunk'. My suspension couldn't be moving enough to cause a full droop condition. I have had coilovers on a previous car that I didn't have enough droop travel. I can tell you that if you were 'topping out' the shocks, the noise would be MUCH louder and the ride would be scary. I don't doubt that it is shock noise, but my guess is valving. Possibly the ride-height valves aren't able to handle such a small movement.
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  #50  
Old 08-16-2012, 04:43 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Agree to all the posts above, however what the Chrysler Technician steted to me was "the self leveling shocks are too short causing this clunking" he doesn't state that they are too short when they are fully dropping. It might mean their standard level under standard load is to short or anything else...
Hell, the technician probably got the explanation from somebody else and might not understood everything by himself. Due that he stated the problem is known and they are working on it I'm confident they will get the issue resolved (hopefully).

To our selfinvestigation; fully agree short, sharp bumps are causing it. But from my understanding the internal valve of the shops starts working when heavy load is causing a sag, therefore a force activating the pumping process. So, I have difficulties to see the internal valve as the reason. Additionally, when the clunk wasn't initially present after replacing the shocks, how can it be the shock. I would thin if it's a construction flaw with the valve it should be present from the beginning.
My initial thinking was more in the direction of the mount (comparable with all the TSBs of the 2011 with standard shocks), also the TSB for the SRT8 with the flash to stiffen the suspension so that the cradle doesn't bounce into the body stops indicates something major in the whole composition of the rear suspension.

@yoda42: interested in your opinion as a mechanic; could other elements of the rear suspension cause this clunking like the crossbar, bushings, cradle etc? I mean there are about 4 different connections from the axle to the frame. Did they replace anything else?

Is there anybody without self leveling shocks who experiences the same clunking?
Do all 'clunkers' have fuel tank skid plates?
Do all 'clunkers' have QT2?
Do all 'clunkers' have a Tow hitch?
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  #51  
Old 08-16-2012, 05:50 PM
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Only the shocks were replaced, it is definitely the shocks
Things need a bit of use before they settle in to there "normal" condition, this is the case with the shocks and why they are quite when new then get noisy with a few km's on them
If I had to guess they have some manufacturing tolerance issues with the internals of the shocks
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  #52  
Old 08-18-2012, 05:36 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Yesterday, I sat in the 2nd row While my wife drove and recognized that the clunk is really load. A call by the dealer gave no news, so today I spent some time trying to locate the noise. For that i removed eveyhting out of the trunk, including the inner molding and sparetire compartment. Then I spent some time in the trunk while somebody else drove the GC around. So, that is what I found;

- it is clunking/rattling on roads with small bumps (like a washboard) all the time. You can hear it in the trunk area on huge bumps like speed bumps though
- upper fender well area is quiet, however there is some noise on the left side
- clunking/rattling is definitly comming from under the trunk area
- both sides rattle/clunk equally loud, but side of noise depends which wheel goes over a bump
- noise characteristic is a damped spring, it is triggered with a pronounced clunk and then quietes down with some rattles
- you can actually FEEL it (the carpet in the spare tire compartment is very thin and while I was moving around if felt the clunks and rattling). I can even feel it on the 2nd row now when you grab some of the mounting points
- we were shaking the car sideways, no clunking
- we were shaking the car in the rear (up and down), no clunking
- exhaust doesn't touch anything

Summary, it needs some sharp thumps or pushes to the suspension to initiate the clunk. From my knowledge it doesn't sound like defect shocks or valves in the shocks. The characteristic indicates to me that something is loose, touching the underbody (or could some weared or defect bushings have the same effect?). It might also be the cradle touching the underbody unintended. Not sure how it could fit with Chryslers statement that the shocks are too short?

Next step for me is to remove all skid plates and check the underbody. I also will check the bushings. How can I identify defect bushings?
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Old 08-18-2012, 06:45 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Count me in as having noisy rear suspension. Notice it in subdivision streets the most. I had a very similar noise on my old WJ Grand Cherokee in the rear when putting aftermarket shocks in. The consensus was that the upper shock bolt that went through the eye was too thin and needed to be beefier.

I personally think it sounds like a shock absorber issue. If they have different shocks on tow pkg equipped WK2s then this would help confirm this.
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  #54  
Old 08-19-2012, 08:07 AM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

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Originally Posted by mistadobalina View Post
Count me in as having noisy rear suspension. Notice it in subdivision streets the most. I had a very similar noise on my old WJ Grand Cherokee in the rear when putting aftermarket shocks in. The consensus was that the upper shock bolt that went through the eye was too thin and needed to be beefier.

I personally think it sounds like a shock absorber issue. If they have different shocks on tow pkg equipped WK2s then this would help confirm this.
They indeed have different shocks, and when our collagues in the Aussie forum changed them to standard, the noise went away. However, they didn't swap the spring which is then too soft (causing a sag) and that brings you a total new suspension configuration, which might eliminate the noise. From my localization attempts, the noise doesn't come frome the rear fender area but from under the car and you can feel something knocking on the body (feels like something is loose). Might be a different problem though.

So far I see following suspensions affected (in order of majority)
- SRT8 (TSB in place; hardening dampers by software update to avoid cradle to bump into bodystops)
- Tow Package equiped Jeeps (Laredo/Limited) (no TSB)
- Standard Suspension (TSBs in place; replace shock mount and grease shock stop)
- QuadraLift (no TSB; very rare)
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  #55  
Old 08-19-2012, 03:05 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Status:
I removed all skid plates, checked all bushings and was looking for points were the suspension or drivetrain would touch the body.

Indeed on the driver fuel tank skid plate, the fuel tank touched the skid plate. So I will see if that could have been the cause (my skidplates are brushed with FluidFilm for rust prevention, so I can see if something made contact). But that has been the only spot.

Checking the bushings was kind successless; all move and show some flexibility but the rubbers look very good and there is no contact from the inner mount to the outer mount.

Checking the drivetrain, exhaust; all fine no touching nothing close by. But I found that the front mount of the rear differential (passenger side) makes some contact from the differential to the body (red & green marks). While there is a lot of space on the rear facing side of the mount (green), the front facing side touches the body via the rubber ring (red). Iti is pretty tight and I am not sure if that rubber is isolating enough.

What I also discovered is something with the rear cradle. The rear cradle is mounted via 4 rubber mounts to the body. All rubbermounts have some space between the upper rubber and the body. The surface of the upper ruber has some pikes. It looks like these pikes touch the body regularly (blue marks). I only did one example picture, but it is the same for all 4 mounts.

It would be great if somebody could compare my pictures with his vehicle and see if that is similar.
Does anybody have some documentation on the differential mount and rear cradle mounts (service manual information?). I would like to know if there are some specific specs or space requirements.
Attached Images
File Type: jpg wk2_underbody.jpg (38.8 KB, 54 views)
File Type: jpg Rear Differential Mount3.jpg (368.9 KB, 79 views)
File Type: jpg rear cradle mount_touch2.jpg (349.4 KB, 63 views)
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Old 08-19-2012, 11:51 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Suther, great write up and appreciate the legwork. I will look under mine and see if it looks the same.
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  #57  
Old 08-20-2012, 03:37 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Quote:
Originally Posted by Suther View Post
Status:
I removed all skid plates, checked all bushings and was looking for points were the suspension or drivetrain would touch the body.

Indeed on the driver fuel tank skid plate, the fuel tank touched the skid plate. So I will see if that could have been the cause (my skidplates are brushed with FluidFilm for rust prevention, so I can see if something made contact). But that has been the only spot.

Checking the bushings was kind successless; all move and show some flexibility but the rubbers look very good and there is no contact from the inner mount to the outer mount.

Checking the drivetrain, exhaust; all fine no touching nothing close by. But I found that the front mount of the rear differential (passenger side) makes some contact from the differential to the body (red & green marks). While there is a lot of space on the rear facing side of the mount (green), the front facing side touches the body via the rubber ring (red). Iti is pretty tight and I am not sure if that rubber is isolating enough.

What I also discovered is something with the rear cradle. The rear cradle is mounted via 4 rubber mounts to the body. All rubbermounts have some space between the upper rubber and the body. The surface of the upper ruber has some pikes. It looks like these pikes touch the body regularly (blue marks). I only did one example picture, but it is the same for all 4 mounts.

It would be great if somebody could compare my pictures with his vehicle and see if that is similar.
Does anybody have some documentation on the differential mount and rear cradle mounts (service manual information?). I would like to know if there are some specific specs or space requirements.
Good news!! Its not the skide plates The noise is still there, also the clunking against the body (which is probably causing the noise).

Somehow I feel JRNYC is right, the suspension lacks precision compared with the noise it might be some worn bushings. On the other hand, my first SUV so no experience with this kind of suspension.

@mistadabolina; thanks I am really keen on a comparision because that is we can eliminate causes. Thanks for spending time on this!
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Old 08-20-2012, 03:54 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

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Originally Posted by Suther View Post
Good news!! Its not the skide plates The noise is still there, also the clunking against the body (which is probably causing the noise).

Somehow I feel JCRNY is right, the suspension lacks precision compared with the noise it might be some worn bushings. On the other hand, my first SUV so no experience with this kind of suspension.

@mistadabolina; thanks I am really keen on a comparision because that is we can eliminate causes. Thanks for spending time on this!
Great work Suther, thanks for the shout out but I still dont have a clue what it could be. I am partial to the load balancing shock theory at the moment. I looked at the diagrams and other research through other forums also and it seems as if the car gets up to load level height on the shock through regular driving somehow, then when you start off at a light it drops ( or thuds ) its way back to normal as if something didnt let it return to normal position. I was hopeful about the rear differential mounts being the cause as well.

Oh I long for the days of having a lift and a snap on toool box full of Craftsman tools!!! GRRRRR apartment living! lol

Anyway I think on my replacement jeep ( ) more on that another time, I will go for a limited 5.7 pretty much loaded all the way with OR1 ( no quadralift which comes with OR2 on the Limited and no NO load leveling shocks. I can put them after I suuppose If I need them. I dont do any towing anyway but was hoping to get my Bike to the track a few times.. that hasnt worked out yet either lol.
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Old 08-20-2012, 06:35 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

My GC is on the service area right now been checked for the rear noise described here.
They already called me today saying my car wont be ready because the tech guy could not figure out the noise.
They have already change the two back shocks in the last appointment with the service tech and let see if they find anything else wrong now.
I am actually getting very annoyed with the noise and I have already let them know I will not the possesion of the GC until they clear the noise. Let see what happens.
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Old 08-20-2012, 06:45 PM
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Re: Wk2 Rear Knocking Noise Aussie GC Laredo

Quote:
Originally Posted by yoda42 View Post
The noise accrues on the black top, unless you are on the worst roads in the world or hitting a speed bump at 80 you will not top out this suspension, if you where the car would be bouncing all over the road, jack your car up and see how much wheel travel you have, this noise comes from minor road defects not major suspension travel, it is the sharp quick movements that cause the rattle/clunk
I have had my rear shocks replaced twice and the noise returns after about 300km on the new shocks
As an ex-mechanic I will state that it is not the shock coming to the end of its travel top or bottom making this noise, it is a problem with the internal valveing of the shock not the length
And yes I have had a very good look at the suspension, I have a 50mm lift that I installed my self
If this rattle/clunk was caused by the shock being to short it would be noticed more off road, I have had our GC off road many times and the noise does not occur when articulating the suspension off road, only on the black top with minor road imperfections where the suspension does not work through its full range of travel
Forgot to say Thanks for that info YODA..
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