• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Rear Suspension - HELP

james21

james21

Cruise Coord
PM 2021
PM 2019
PM 2014
PM 2012
SM 2011
SM 2008
SM 2007
SM 2006
SM 2005
SM 2004
SM 2003
Full Member
Joined
Jul 18, 2002
Messages
6,075
Location
Cooperstown, New York
I've had this problem with my rear suspension for a long time, and I cannot figure out why it continues. The rear end tends to bottom out, mostly offroad, but also going over bumps on main roads. I honestly don't believe the bed is overloaded. I've had the rear coils replaced twice in the past 3 years, and they seem to improve it some but not much and not for long. I've looked around, and no one makes a HD coil for the Avalanche, and the only option I can see is Air Bags, however that is going to be a custom job due to the 6" lift.

Any Help is appreciated.
 
This may be a stupid question but how do you know it bottoms out? With a 6" lift it seems very hard to bottom out. That is a lot of travel before bottoming out.
 
What shocks do you have on the rear James. ?
 
raiderron said:
This may be a stupid question but how do you know it bottoms out? With a 6" lift it seems very hard to bottom out. That is a lot of travel before bottoming out.
Click to expand...

I know it bottoms out because I can hear a very audible SLAM! And so can everyone else around me.

I've got Bilstein 5150's in the rear, they don't make them any longer, they had a small piggy-back reservoir on them, they could be shot, but my mechanic seems to think they are fine and I'm thinking he's nuts.
 
The shock question does make sense to me if they may be too long of an application for a higher lift that could bottom out easier because they are shortened when mounted on the shorter lift. If of course they are shorter than needed for the lift that would explain maybe not enough travel that would limit the suspension travel. Shocks are designed to absorb spring action and even provide some additional lift at the rear in some instances. Maybe the shocks are the correct application for the 6" lift and they are just shot or faulty causing the noise or feeling of bottoming out. Could the slam noise possibly be coming from somewhere else at the rear where something is impacting the axle area when the suspension is compressed? ???
 
I can see where the bump stops have been impacting, so thats another indication. Trust me, this has been going on for quite a while.
 
That's the other thing. If bump stops are compressing badly then that backs up the bottoming out theory. That is still quite a lot of compression travel, 6" lift, to compress to that point. It sounds like the shocks are just not dampening at all. Does it only do it over larger bumps?
 
Did the RCD 6 kit use shock extenders. ?
 
I have loaded 2000 pounds i my truck and did not bottom out.

Something is wrong or something else is banging...
 
Well, I'm going to takes a day this weekend and unload the entire bed and see if it still does it. I got a place in town at a local car wash that does it every time. So I'll know more.

The RCD system does use extenders, I'll check to see if they are on.
 
How much load do yo uhave in Bed?

Maybe it something in the lift kit hitting at a certain point and not really bottoming out.
Maybe something loose or bent or not installed properly?


To bottom out you pretty much have to have the rear end sag a bunch of inches...and even then it will ride on bump stop which when they hit do not make much of a noise... they are rubber...
 
I can push down on the rear bumper to the point that it hits the bump stops
 
raiderron said:
That's the other thing. If bump stops are compressing badly then that backs up the bottoming out theory. That is still quite a lot of compression travel, 6" lift, to compress to that point. It sounds like the shocks are just not dampening at all. Does it only do it over larger bumps?
Click to expand...

Lift kits relocate the bumper to within stock distance. He isnt compressing the suspension 6 inches, rather only about 2-3
 
There ya go. Take it to a shop and drive it up on a drive on rack and then compress the rear while inspecting it underneath.
 
Taking it to a shop on Tues, just want to get rid of the slam, it's embarrassing.
 
I'm guessing the springs are bad since you actually drive your AV, how many miles to you have on it now.
 
142500. But the springs were replaced 13 months ago.
 
From what I remember of your AV it did not look like you added that much weight to the back of it. So maybe go with a longer shock and remove the extension.

I would have said longer progressive spring, but I could not find one for the AV either.
 
You suggested possibly the spring- under normal driving conditions, how often are the springs needing replacing... and how can you tell?  Lack of recoil, or too much?  Go with the same brand of the shock so they'll work better for him?
 
TX619er said:
You suggested possibly the spring- under normal driving conditions, how often are the springs needing replacing... and how can you tell?  Lack of recoil, or too much?  Go with the same brand of the shock so they'll work better for him?
Click to expand...






I for one did not understand your whole question so I will take it piece by piece and try. The OP said he replaced the springs twice in the last 3 years for the same problem. He said it seems to improve but not for long and wants to figure it out once and for all. Lack of recoil could be tied to a bad spring or a shock not allowing the correct travel at the correct time. Too much recoil typically means a worn out shock because shocks are designed to control spring action. Want to be sure the chosen shock allows the spring full travel at the needed times without the shock itself bottoming out. He has a 6" lift so obviously has shocks for a 6" lift unless they are the wrong shock somehow. So did I understand you right or am I still confused?
 
You answered it- just trying to pull from his question and your answer(s) some of what I'm looking for too. I know my shocks are shot- am wondering if I need to replace springs too.  Thanks for the input.
 
You folks have not seen his truck it's lifted with a big winch and other toys on it. I'm thinking his needs a heavier spring and shock. I think with a longer spring minus the extension he would not bottom out so easy. From what I read his kit has a 6 inch coil extension and shock extension.

But I'm no lift expert so I'm guessing at this.
 
It would be best if he could find a progressive spring that still gives him his lift he is looking for. Progressive meaning, I know some of you already know-sorry, as the spring compresses it tends to stiffen and not allow a "bottoming out feel" and handles weight better during compression. You might think it would give a harsher ride but not really until at the last of the compression of the spring.  To answer TX619er, shocks can wear out from age, use if it is excessive over a short period of time, quality shocks cool better internally and last longer and tend not to leak prematurely allowing for better shock life and use because the correct fluid stays internal for the dampening plates to do their work. When replacing shocks always think about how you tend to use them and buy accordingly. The springs may not be worn out but are certainly worn and if you plan to keep the rig and want to do the job once then if you can afford it, buy new springs and again buy the springs that will work for what you plan to use them for. I bet there are plenty of older threads addressing this or guys on here that know what to recommend to you for your application. Suspensions are very important for any vehicle. Don't matter how good or fast it runs if your don't have the suspension and brake system under the rig to handle it.
 
Well I had some time today and actually just finished 20 mins ago, took everything out of the bed and took it for a quick drive. The drive was inconclusive, it didn't bottom out at a certain place it has in the past, but I also didn't hit it fast enough, because I've gotten used to going slow for it. Also after taking everything out, I know there is no way that I'm even coming close to exceeding the weight limit. Maybe 600-700lbs, if that. On a side note I did find 30lbs of used or dirty microfiber cloths :9:. Its better organized now, with stuff I need or will get used more often close to the front, and other stuff at the back.

But will still have to wait till Tues to find out if it is the rear shocks that are shot. Thats really my only guess at this point. Also Byron, I don't think my coils have an extension on them, the shocks do, but I don't think the coils do. Maybe my kit didn't have them.
 
You must log in or register to reply here.
Back
Top