Rough ride

Tiny
UPMM019
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  • 2015 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 176,000 MILES
I purchased the vehicle listed above LTZ model used, last fall from my local GM dealer. Was told it had the full inspection and it netted replacing the tires, cooler lines that were leaking and replacing a key fob.

This past week it tripped a check engine, so I had it looked at today and found out the check engine was the least of my worries.

I was advised the check engine was tripped by it sensing a higher level of alcohol in the gas. I had never heard of this, but they said there was nothing to be done as the check engine had turned off after I had filled it up before taking it to be looked at.

I asked them also to give it an oil change and go back over it again to find anything wrong as I am planning on a trip down south and didn't want any surprises. I did mention that I noticed it was sluggish, didn't get all that great of gas mileage and it rode rough.

The tech who called said they didn't find anything wrong and attributed the sluggishness to the supposed bad gas; though I didn't buy it as it has been sluggish the entire time I had it, but I wouldn't have noticed it on a mere test drive. The tech noted no other issues other than stating the shocks or struts were all bad.

I was quoted $2,250.00 for the front and around $1,800.00 for the rear.

Could this possibly be? He mentioned that they were not hydraulic but rather electronic, thus the price. If that is the case is this the only option for repair or is there a delete option like the ones that had air ride struts, etc?
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Tuesday, May 3rd, 2022 AT 3:09 PM

22 Replies

Tiny
STEVE W.
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The alcohol content issue is common on GMs that have flex fuel engines. The most common cure is to use a scan tool to take a sample of the fuel, test it for alcohol content using a simple test and then resetting the alcohol content back to the baseline. The easier method is to just reset it and let it relearn the content after the reset. Having it wrong can cause a myriad of drivability complaints as the system assumes the content is correct and will adjust the various items like timing, fuel mix and cylinder deactivation to match the supposed running conditions the high alcohol mix needs. However, if that alcohol isn't actually there it will run rich, smell and run rough and act sluggish. The colder weather, and winter blended fuels may have masked it a bit. The reset takes care of that.

For the suspension I suggest getting a second opinion at another shop. The OE parts are very expensive, and you can get aftermarket units cheaper, but they are still close to $300.00 each for the rears and $400.00 each for the fronts. They could be leaking or damaged but unless you are actually feeling that or the truck wallows around while you are driving, they may be fine.
I had a transmission replaced in a vehicle under warranty and the shop tech told me that "both front struts are gone because they leaked out" except what he saw was actually the undercoating oil I have used on vehicles for years.
In your case you could easily slip under the truck and look at the shocks and struts, if the parts around them are all dry but they are oily, maybe they are leaking, wipe them off and see if it returns. However unless you think it rides bad or seems to bounce or wallow I would suspect the diagnosis. There are ways to remove the system, but it takes a dealer to remove the option code from the system to keep the active suspension failures from showing on the dash if you remove them.
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Wednesday, May 4th, 2022 AT 9:50 AM
Tiny
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Yes, they did the scan tool and sample of the fuel. Where I live, I use the 87 grade which has 10% ethanol. I never use any flex fuel. Not even sure what that is.

The slightness of a bump on the road you feel everything there is no dampening. Where I live, I know where most of the big bumps are, so I drive to avoid them since it does not absorb them at all.

Clearly, they knew about this issue and chose not to disclose it. GM manger offered me $1,000.00 towards the $4,100.00 and I told him no thanks.

A good negotiation is where both parties feel like they got screwed and this is not the case so they can keep their $1,000.00 again just stating my opinion of the matter.

I am currently looking at other options, but I live in a small town - I trust no one.

Will most likely end up doing it myself but will need an alignment at the minimum I believe.
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Wednesday, May 4th, 2022 AT 10:00 AM
Tiny
STEVE W.
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The ethanol issue happens even if you only use straight no booze gas. It has to do with how the fuel sensor detects the alcohol and how it measures the content. Nobody has so far pinned down a definite answer because it seems to occur regardless of the actual alcohol content.
Your description of the ride doesn't sound like a shock or strut issue but it just having a truck suspension design under a large heavy vehicle. If I remember that system can be adjusted for different ride quality. However, you might want to look at https://www.shockwarehouse.com/news/gm-suv-suspension-decoder.cfm
to get a better idea of what you have and other options.
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Wednesday, May 4th, 2022 AT 11:04 AM
Tiny
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I am not finding any of those codes on my sticker mentioned in the link you shared.
The three Z codes one is for solid body color, trailer package and then Magnride suspension.

I ordered a set of Monroe struts for the front - Monroe Shocks and Struts Quick-Strut 139104 Strut and Coil Spring Assembly

I ordered these rear shocks (Monroe 911506 Reflex Monotube Shock Absorber) but then just cancelled as after looking at the rear shock there appears to be some sort of port on the side that make me think the rear is air ride?

I plan on using the bypass kit from shocksims - : Xineering LLC.
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Thursday, May 5th, 2022 AT 6:13 AM
Tiny
STEVE W.
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Okay, you have the Z95 option which is the "fancy" version of Magnaride. That is the fully electronic controlled suspension option. It is the same thing they have on the up-level Cadillac's. It uses a controller to activate the fluid inside each shock, no valving involved. That is why you have the connector on the shocks and a similar one will be on the struts.
You can use the base level parts to replace them and use the bypass kit to shut the system off.
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Thursday, May 5th, 2022 AT 6:59 AM
Tiny
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Steve,

So, with the "base level" parts noted below, beyond an alignment is there anything else one would need to do after the Magneride was replaced?

Struts: Monroe Shocks and Struts Quick-Strut 139104 Strut and Coil Spring Assembly
Shocks: Monroe 911506 Reflex Monotube Shock Absorber

Xineering LLC stated their bypass is plug and play no need for a scan tool, etc.
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Thursday, May 5th, 2022 AT 7:03 AM
Tiny
STEVE W.
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Once the parts are replaced, a quick front end alignment should be all that's needed. I would probably unplug the connectors, shoot some dielectric grease into each one and put a wrap on them, just in case you change your mind or sell it and that person wants to go back. Plus it would help prevent anything happening if the connector touched something else.
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Thursday, May 5th, 2022 AT 11:17 AM
Tiny
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Sounds good I did schedule my alignment for next week.
I have read other people who did the same set up saying it was a good replacement but would you say that would be the case over an OEM Magneride?
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Thursday, May 5th, 2022 AT 11:19 AM
Tiny
STEVE W.
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In OEM condition the Magnaride is very nice but if you have the OE level scan tool you can also play with the calibration to make it softer or stiffer. The Cadillac version gets the soft ride, the others get more truck like settings. GM could have easily made it user adjustable, but they didn't do anything until the 2021 versions, and even then, it's minimal.
Owning a scan tool that can adjust it makes a difference.
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Thursday, May 5th, 2022 AT 11:35 AM
Tiny
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So today I went to look to see what it would take to replace the rear shocks. I learned that the shocks that are on the vehicle have an air line. The Monroe rear shocks I ordered do not. I found these shocks on Amazon (https://www.amazon.com/gp/product/B014RFE8RO) which appear to be a replacement and fit the 2015 Suburban LTZ with air but now I am learning that I need a scan tool to replace and set them up correctly. I do not have a scan tool.

Since I am not much of a mechanic, I am now starting to lean to sending the stuff back and just have the dealership do it but I cannot swing the $4,100,00. are there alternative Magnride solutions that are not OEM but satisfy as an adequate replacement? The dealership said they would use the parts I had to replace, which is very odd, they would even allow it and they would charge about $700.00 to install and complete an alignment.
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Thursday, May 12th, 2022 AT 9:08 AM
Tiny
STEVE W.
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Okay, if yours have an air line it must have the automatic leveling and Magnaride as well. That is about the most expensive system GM offered at the time. The aftermarket doesn't really offer much other than ways to eliminate it, which is what the parts you have should do.
The dealer will use your parts, likely because they cannot get the OE parts in any reasonable time and want your business.
The only reason for a scan tool would be to reprogram the suspension control module after you removed the OE magnaride parts. That is what the piece you bought from Xineering should do.
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Thursday, May 12th, 2022 AT 10:31 AM
Tiny
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I was of the understanding if I use the ACDelco GM Original Equipment 540-1675 Rear Air Lift Shock Absorber that a scan tool is needed to cycle the air pump before lowering the vehicle, otherwise there could be damage to the new air shock and pump. I am just going off what my internet searches have said.
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Thursday, May 12th, 2022 AT 10:35 AM
Tiny
STEVE W.
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That would be if you replaced the suspension with OE parts. You mentioned you were using nonstock parts that didn't use the air system. If you intend to keep the auto leveling system intact and use OE parts, the scan tool would be used to set the initial height if you replaced the control module or a height sensor. I don't think I've ever done that when changing out just the rear shocks themselves.
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Thursday, May 12th, 2022 AT 11:47 AM
Tiny
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Yes, once I realized it had the air shocks, I ordered the new set that is air (https://www.amazon.com/gp/product/B014RFE8RO) so you are saying these would be OEM? or no I am confusing myself as to what is OEM and not. Does the Z95 suspension rear shocks have air and Magnride electronic functionality or is the electronic only on the front? Rear is Air only.
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Thursday, May 12th, 2022 AT 12:10 PM
Tiny
STEVE W.
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Z95 has Magnaride at both ends plus air at the rear for the auto leveling. If you only have an air line to the rear you might want to check it closer, it almost sounds like someone already changed some parts. Your dash sticker shows the Z95 option which is 4-wheel Magnaride.
Arnott used to make some that fit but I haven't looked in a while.
These look to be Z95 compatible, but you need to see what parts of the system are still there before buying them.
https://www.amazon.com/Genuin-Absorber-Kit-Part-23487280/dp/B0128HZBVK
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Thursday, May 12th, 2022 AT 12:43 PM
Tiny
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Steve - I have kept looking and stumbled across Luft Meister on Amazon. They appear to replace OEM for the Z95. Cost wise these are a tad bit cheaper than the struts/shocks/shocksim delete kit. However, I am not sure which route would be better... try these Luft Meisters or keep with doing the delete and using the Monroe 139104 / ACDelco 540-1675 and the ShockSim Delete kit.

Front: https://www.amazon.com/gp/product/B09Q2VW9D9/ref=ox_sc_saved_title_1?smid=A1JOW3LPPQQJML&psc=1

Rear: https://www.amazon.com/gp/product/B07WD36VY7/ref=ox_sc_saved_title_1?smid=A1JOW3LPPQQJML&psc=1

Any advice between the two?
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Thursday, May 12th, 2022 AT 8:17 PM
Tiny
STEVE W.
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The issue I would look at first is if you still have the entire 95 system on the truck. You want to verify if you have the control module and wiring before you buy the parts. I'm wondering if you have the Magnaride parts up front and only the load leveling in the rear, which could give you a real strange ride that might explain the problem.
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Thursday, May 12th, 2022 AT 8:54 PM
Tiny
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My last post is not appearing. I am not sure what is wrong. Did you see the post and my query about the Luft Meisters?
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Thursday, May 12th, 2022 AT 9:02 PM
Tiny
UPMM019
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Steve, I have kept looking and stumbled across Luft Meister on Amazon. They appear to replace OEM for the Z95. Cost wise these are a tad bit cheaper than the struts/shocks/Shocksim delete kit. However, I am not sure which route would be better. Try these Luft Meisters or keep with doing the delete and using the Monroe 139104 / ACDelco 540-1675 and the ShockSim Delete kit.

Front: www. Amazon. Com/gp/product/B09Q2VW9D9

Rear: www. Amazon. Com/gp/product/B07WD36VY7

Any advice between the two?
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Thursday, May 12th, 2022 AT 9:07 PM
Tiny
STEVE W.
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They look like they would work. I never heard of them myself. I would go hunting on your truck first though and verify that the rest of the system is there first.
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Thursday, May 12th, 2022 AT 10:42 PM

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