07 Denali Suspension - What do I have, is it working?

I looked through some of the forum posts on this and it just talks about replacement parts for the most part.

My question is, what suspension system do I have and how do I find out? I know I have the airbags in the back and a compressor (that I can hear running when I start up the truck) but when I look at the front suspension I can't find any airlines so I'm assuming that it's not air in the front? is there a magnetic/electronic stabilizing system up front on these Denalis?

Main reason in asking is because I'm trying to determine if my system is still working properly or if I'll need to replace it. When getting my tires changed out at the local tire shop they mentioned to my wife that the suspension was leaking in the front and I'm not sure what is driving them to believe that. I looked over the system and let it run and sit and checked for minor leaks and wasn't able to find anything visible/audible. When looking at the front I couldn't determine what type of suspension it was to even start looking for any issues.

I THINK that all Denalis have autoride (someone will chime in and affirm or deny this). I have autoride on my '09 Tahoe LTZ. The compressor only sends air to the REAR shocks (to level the truck, since you can really only cause the rear of the truck to sag by adding weight there). You COULD have a leak in the front shocks (I did), but you should also get a suspension warning message on the DIC if it really craps out on you.

Can you explain the noise you hear at start up? If it is a noticeable almost light grinding noise, your compressor could be bad... Happened to me. You will hear it even if it is working fine... but it is more of a noise you hear inside the truck, almost like a vibrating noise... like you hear the compressor kick on but only hear it because it is mounted to the truck... if that makes any sense. Should not be very loud...

One way to check if it is working is to feel the airbags in the bag... just look under there, pretty easy to locate... squeeze the bag and see if they are inflated... then throw a trailer on, or load the back up with whatever you can (maybe 2-300 lbs to be able to feel a difference. Then squeeze your airbag again after you drive around the block with it loaded... You should feel a difference in the bag.... if not, and you are getting a louder than usual grinding noise from the compressor, it needs a new compressor.

It was easier for me to diagnose it when mine went bad, because I was able to listen to my dad's escalade at start up/inflation and it was easy to hear that my compressor was bad. Easy fix, i see it on GMpartsdirect for $278 now... pretty easy to get to... right on the rear side of the drivers side wheel well. Behind a small plastic protective housing, maybe 6"x8"... plug and play wires, and small air lines... you will be amazed at how small these air lines are!

Hope it helps...

KMelony, kind of what I thought. So how did you determine that there was a leak in the shock assembly up front?

bauer, same as you explained...you can only hear the compressor because it's attached to the truck. I don't have a concern with the rear suspension. The tire place said the front suspension was leaking and I wasn't sure how they could determine that since there wasn't any visible damage or anything to it and obviously no hissing since it's not an air suspension up front. I did find the compressor while doing my tire rotation this past weekend and took a look. not bad to replace any of it, just gatta take your time I guess. My hope is that it will all last another year or two so I can first spend the money on swapping out the suspension on my F250. haha.

mccullionj said:

KMelony, kind of what I thought. So how did you determine that there was a leak in the shock assembly up front?

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I seem to remember my local mechanic telling me that it was leaking -- and then when we explored lowering the front, he said the unit "came apart in his hands" when he initially unbolted the strut. I have to assume that the struts are oil-filled, and so that must be what he saw leaking. Again, that's just my assumption -- and I'd assume that your mechanic saw fluid as well.

The struts are oil filled. I replaced both on our Denali and used an impact to get the nut off the top of the strut. You should not do that if you need to reuse the strut. It will unscrew the rod from the strut body and let the oil out. The oil has a dark color (after 65k mi) and would be fairly obvious if a seal, o-ring, etc failed, allowing the oil to seep out.

I replaced the struts because the left side sounded like a kid's rubber bouncy ball in a tin can. They were about $270 each, shipped from Rock Auto. GMPartsDirect.com is about the same price. It will just take longer to ship.