GL450 rear end shifts sideways over bumps
 

Hi Everyone,

first time posting here and I've done my best to search through all the previous posts to find my answers, to no avail lol!

Just got a used 2008 GL450 4matic with 79k miles on it. Airmatic, without ADS and without enhanced off road. Bought it privately and the bouncy ride was apparent after driving it for a day or so. I then noticed one of the front struts was losing air so took after turning the car off so I took it to my local MB dealership who diagnosed and replaced the front drivers side strut. Great, that's it I thought but the ride quality didn't seem to change at all. The best way I can describe the problem is that when one of the rear wheels goes over a bump in the road the rear end shifts sideways. It's quite disconcerting, I can deal with it but it freaks my wife out, she doesn't want to drive the car on the freeway as it feels unsafe to her. It happens at low speed as well as high and in addition to this the ride is on the bouncy side generally. So I would like to know a couple of things, is a bouncy ride 'normal' for this car and is the side shift indicative of a failing rear air spring and/ or and rear strut?
Also is there any way to check the rear spring/ struts? The ride height doesn't drop after its turned off (which means the struts would be okay I would think) but maybe the springs need replacing?

This is my first car with Airmatic so I appreicate any insight anyone can give!

ive read your post a couple times since yesterday. I'm having a hard time trying to imagine that happening. is there anyway you can take a video of it happening?

Mine did that and it was a bad shock.

Cant really post a video as it's more of a feel thing when driving it. What I imagine 'could' be happening is this. Go around a corner at speed and the inside rear wheel goes over a bump, it doesn't react well to the bump and the car feels like it oversteers sideways. Would that be a strut issue or a spring issue with Airmatic? Is it best to replace both struts and/ or springs if one is defective? Any way to check for defects (they don't drop at all when it's turned off)

Try swaying back and forth in an exaggerated motion at a safe speed and see if it feels soft on one side. It is either a bad shock or control arm with the shock being the most likely culprit.

Thanks, I'm going to try that BlownV8, part of the problem is I don't know what 'normal' is on this vehicle, my last SUV was a Porsche Cayenne and they are very firm

It should feel obvious.

It is one of three things normally

1. Bad shock
2. Asymmetcal rear bags (i.e. One replaced but not the other)
3. Bad airmatic height calibration (i.e. Truck is level, but it was achieved by overinflating certain airbags in leu of other corners)- this is very common. Pressures should be checked in all four corners and hey should be fairly equal for each pair side to side.

That sensation is almost always a bad rear shock or two. It probably would hurt to get a four wheel alignment also.

Thanks everyone, I checked the rear airbags and they're fine, I'm booking it in to my local independent shop to get the rear struts replaced next week.

please let us know if the new shocks solve it

Hi Everyone, the fault was on both rear struts. The rear airbags were fine. One strut was completely jammed solid (behaving like an additional air bag I guess) and the other was 'sloppy'. Hence the reason for the weird behavior and 'skipping' and wallowing over bumps. I'm glad the problem is finally fixed, I got it done at an independent I trust, it's odd to me that my MB dealer didn't spot it on the road test they claim they did only a few weeks earlier as the bumpy ride was defintely there when it went in. Rides like a dream now, feels safer on the freeway than on surface roads which is comforting. I'd be happy taking the car on the Autobahn now anyday, thanks again everyone!

By the way blown, I tried that on a straight road about 45 mph, very disconcerting lol.

Yeah, when a shock goes out, the car can feel a little uncontrollable. Glad you got it sorted.

Which Brand of shocks did you choose?
 

I have 2009 GL550 with the symptom of a rear bump steer. I believe one of the rear shocks is locked up and acting like a spring.

I see there are at least 5 options to replace the Airmatic w/ADS shocks
1. Genuine MB $$$$$
2. Bilstine $330 each
3. Arnott - new with sensor bypass to eliminate ADS warning and feature $260 each
4. Arnott - remanufactured with ADS still enabled ($206 +$100 core charge) each.
5. Made in China - $95 each

I am leaning towards Arnott remanufactured.
What is your experience?

I installed new rear Arnotts and weird hopping around was eliminated.
 

Non ADS. Bought direct from Arnott. Didn’t see an option for reman.
If Arnotts don’t still have lifetime warranty I would get Bilsteins from Rockauto and save $80...probably should have anyway as I doubt I would benefit from a lifetime warranty either.

Exactly my thoughts. My original ones lasted about 12 years. I just replaced them yesterday with Rockauto $135 each. I thought about getting them from FCP euro but I didn't think I will ever have to replace them again. So wasn't willing to pay around 100 extra just to have the option to get another one free. If it would be air bag, then it would make sense. but a shock is a shock and usually has an expected life.

Hello:

I have the same issue.
Did you end up solving with struts and not airbags?
What struts did you replace with?
Any insights appreciated

Hello:

I have the same issue.
Did you end up solving with struts and not airbags?
What struts did you replace with?
Any insights appreciated

I too had the same issue.

Dealer first said it was my tires. I was planning on replacing them in the coming month, so I replaced them, but same issue.

Dealer then said it was bad alignment. I paid the dealer for an alignment and the issue was still there.

Since the dealer seemed to be having a hard time diagnosing, I put the vehicle on my neighbor's lift and noticed both rear hydraulic shocks were leaking. I replaced both hydraulic shocks with OEM Bilsteins, both tie rods, and both lower shock bushings. Issue was then gone and truck drove well.

Good luck!.

Since the dealer seemed to be having a hard time diagnosing, I put the vehicle on my neighbor's lift and noticed both rear hydraulic shocks were leaking. I replaced both hydraulic shocks with OEM Bilsteins, both tie rods, and both lower shock bushings. Issue was then gone and truck drove well.

Do you have any records from your purchase? Shocks are easy but not sure where to get bushings and tie rods.
Also, is yours a tow vehicle. Mine (2015 GL350) was purchased used but was a nanny's grocery getter. Had never
been off road and not equipped to tow.

Rear shocks will fix the issue.

I replaced rear air bags (easy and cheap). that just fixed overnight sag. Did nothing for handling.

I finally found the real solution. I went to a new alignment shop and he showed me about 3/4" play in the steering rack bushings. To see it you need the car on the rack, engine running, driver in seat to turn wheel from side to side. We stood under the car and we could see the whole steering rack shift left to right when the wheel is turned. The bushings are relatively inexpensive but there is a lot of labor to replace them. I think it was about $700 with parts, labor and alignment. Once the bushings were replaced it is back to being an enjoyable ride. :-)

I had the same issue on my GL 350 ~ it’s the tires, I went from 275/50/20 to 285/50/20 tires and problem with rear end shifting on bumps, is gone and rise quality is now like GL should be

There’s gotta more to this story than just going 10mm wider and 5mm taller sidewall on the tires.