Rough, bouncy ride

So I have a 2008 GMC envoy denali 5.3L with a few aftermarket mods and I am having issues with the rear suspension. It sags down to the tires in the rear when off at times, and other times it will be at proper height. When I shut it off, I usually hear an audible hiss, but if I start it up it fills back up. When I reset the comp, afterward it will ride perfectly normal, but as it relearns it gets progressively worse until it reaches the point where when we hit a bump, everyone in the car gets jolted into the air-becoming almost uncontrollably bouncy as you drive. Though I havent ever swapped an air compressor and rear air springs, I have considered this if that is actually the issue. I have another envoy that is an 2002 slt by that has coil spring suspension that is immobile due to trans issues and was considering taking that suspension and bolting onto the 2008 but I'm sure the air shocks arent compatible to put on the 02 until its fixed. Does anyone have any suggestions or remedies to this issue? Is this an isolated problem or common?
 

littleblazer

Gold Supporter
Problem is very common actually. I believe the shocks and springs are 100% interchangeable so all you would have to do is remove the rear sway bar and drop the axle down. Spring compressor not needed for that swap, there is enough room to slide them out. The only thing you'd have to do is unplug the compressor so it doesn't burn out I believe.
 

TequilaWarrior

Well-Known Member
If the "hiss" is coming from the air compressor - you can remove it and put in a "T" fitting, joining the schrader valve in the cargo area with the air lines going to the left and right bags.

I mention some of this in this thread: https://gmtnation.com/forums/threads/air-suspension-acting-weird.19383/post-573568 with a little more info further down, including a picture. It may be easier to do this instead of the spring swap - although a spring swap should be the long term goal. "T"ing would allow you to keep one running while also being able to fix the tranny problems in the other one. If you do the "T" mod, you have to remove the compressor. Also remove the fuse for the compressor.
Either way, good luck.
 

16vcabman

Well-Known Member
A hiss is air escaping and can be bags, which by this time could have failed. It really depends on how much you want to keep the air ride. Rock Auto sells Arnott bags for around 87 dollars. Do both because if one is gone the other is not far behind. If you want springs just support axle and pull lower shock bolts. Lower axle until spring fits. You don't need to replace shocks if putting in springs.
 
OP
OP
A
If the "hiss" is coming from the air compressor - you can remove it and put in a "T" fitting, joining the schrader valve in the cargo area with the air lines going to the left and right bags.

I mention some of this in this thread: https://gmtnation.com/forums/threads/air-suspension-acting-weird.19383/post-573568 with a little more info further down, including a picture. It may be easier to do this instead of the spring swap - although a spring swap should be the long term goal. "T"ing would allow you to keep one running while also being able to fix the tranny problems in the other one. If you do the "T" mod, you have to remove the compressor. Also remove the fuse for the compressor.
Either way, good luck.
After successfully installing the "t" I noticed that there was air coming out of a dry rotted spot on a shock, that not always leaks but most of time...any suggestions on how I could plug this leak until able to find permanent fix? The leak is barely visible when sprayed with soap water...
 

Wooluf1952

Well-Known Member
You can try putting a patch over the hole. The same as patching an inner tube. If you clean the area good enough it might hold for a while.
 

TequilaWarrior

Well-Known Member
After successfully installing the "t" I noticed that there was air coming out of a dry rotted spot on a shock, that not always leaks but most of time...any suggestions on how I could plug this leak until able to find permanent fix? The leak is barely visible when sprayed with soap water...
I'm going to presume you mean airbag/spring instead of shock. Like @Wooluf1952 said, maybe try a patch. I'm not sure if an inner tube patch with the right adhesive would stick well enough to fix your problem. It might be necessary to more or less completely unload the rearend and let out as much air as you can without distorting the bag too much before trying to patch it as even the smallest leak would apply pressure from the underside of the patch and cause it to fail before curing.
Mine has a small leak. My leak is mall enough however that I go weeks without putting air in. I've been tempted to add "green slime" - but haven't because I don't know if it will go where it needs to and do its job without plugging up the lines. If that were to happen, game over, new spring time.
Glad to hear the t-fitting fix worked - good luck with the patch. Let us know how it turns out.
 

Wooluf1952

Well-Known Member
Agreed. Probably the best time to patch it would be when it's down to the bump stops. Then remove the fuse to the compressor. Jack it up. Put it on jackstands. Apply the patch and wait for it to dry. Also. I was kind of confused too about the air shocks/air bag statements.
 

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