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Discussion Starter #1
Well I got the '04 Dually 4x4 a couple weeks back and I'm still trying to get the thing to ride smoothly when unloaded. Of course it has the helper springs on top of the leaf pack and the overload spring below. Something back there clunks over the big bumps and the whole rear axle seems to bounce a lot. I installed velvet-rides and RS9000s and adjusted tire pressure and have gotten it quite a bit better overall, but since the velvet-rides make the rear of the springs a little closer to the helper spring stops, there is even more slapping and banging over mid size to large bumps.
I am considering removing the helper springs and possibly the overloads and adding some air-bags. Any thoughts on whether this will give a softer ride?
Thx,
jeff
Edited by: ZZ4x4
 

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I do not have a dually but I do have air bags and I keep just enough air in them as to arch the springs where they do not hit the lower heavy spring on moderate bumps and I think they make the ride smoother. You could remove the stops for the overload springs and probably smooth out your ride some and if you add air bags they would make up for any loss of load capacity. Many poeple will tell you the air bags will leak or may explode at just the worst time but I have run them for years and have never had that problem. I do run on the gravel alot and if I get my thuck real muddy or gravely I will wash off the bags (when I get around to it) to remove the abrasive material.
 

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If you have not already - put on a set of Bilsteins and then the air bags. I put the Bilsteins on at 3000 miles and it made quite a difference. The air bags went on at about 800 miles later - just 8 psi lifts the rear about 1".








2004 GMC 2500HD EC LB D/A (LB7); GMC bed liner;Air Lift Super Duty air bags; Michelin LT265/75-R16 LTX M/S ;Luverne Running boards; Bilstein shocks; Delvac 1300; Isspro gauges.
 

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ZZ, you can remove the overloads if you are not towing, and you can install airbags which will ease the ride alot. Also you might want to consider some bilsteins or ranchos and that will also make it better. Or if you are drastic about it you can even go down to a half ton spring, have seen a few people do it but then you will not be able to use the truck for anything. But it will ride better. Just my two cents.
 

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Discussion Starter #5
Just for the archives... PROBLEM SOLVED!!!!


The final config of the rear suspension is as follows:


-Rear helper leaves removed.


-RS9000x shocks installed and set at 5/8 stiff .Use shocks listed in Rancho app guide since they are 2" longer than stock, which is important since the stock shocks are actually too short and bottom out over deep potholes.


-Velvet ride shackles installed. Note, the velvet rides made the ride worse when used in combination with the helper springs as they allowed the rear helpers to contact the hard stop over even minor bumps.


-Tires set at 65psi


The truck rides amazingly smooth now. The rear suspension is actually more compliant than the front. Going over a speed bump, the front gives a firm but compliant thump while the back just goes cushhh. Ahhhh. Nice. Rides much better than my stock 2500HD.


May add air-bags later if needed for heavy loads.


Hope it helps others....


JeffEdited by: ZZ4x4
 

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What do you mean when you say bottoming out?? Are you talking about on the compression side or the rebound side? I highly doubt that you would bottom out on the compression side unless you had a heavy load in the back. The shocks are not bottoming out, if the shocks were over extending or bottoming out, they would be damaged either by knocking the o-ring out of the bottom of the body, or pulling the shaft right out of place, and when you say two inches longer what do you mean? If the shock is longer you must of either had to change the mounting position, or the body itself is shorter, but that would limit travel as well. Remeber the shock can only travel the length of the body. If you want to check your travel, put a tie rap around the shaft right up against the shock body and go for a ride. If you are bottoming out, the tie rap will break off, if you arent, then you can see how far you travel. I think you are most likely feeling the difference due to adding a high pressure gas filled shock which can take the force much better than the stock oil shocks. If you want anymore info let me know, I rebuild many different types of racing shocks.
 

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Discussion Starter #7
Emerick, Sorry, let me clarify. By bottoming out, I'm talking about on the extension. As crazy as it sounds, the shocks were indeed limiting the downward travel of the axle. There is another post of mine near this one about stock rear shocks being all wrong. When you look at the rancho guide, there are specs for compression, extension and travel. The travel of the "recommended" shocks is 2" greater than what you will measure on an actual factory shock. I measured em sitting on my garage floor. I agree the stock shock will not last in this type of environment, as over extending a shock against it's piston will destroy it. I'm only stating what I measured and checked with my own two eyes and hands
 

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so if you measured the distance from the bottom of the axle tube to the bump rubber, this distance was more than the available shock travel, and u werent hitting the bump rubber, you were slamming the shock body to the mount?
 

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I realize the suspension in your truck is different than mine, but for 2500HD owners there is no need to worry. The amount of shock travel of 6 inches is more than the distance from the axle tube to the bump stop which is 5.25 inches. And remember when you are measuring the shock travel, you can't really figure it out by measuring the amount of shaft showing at ride height because when the rear end moves up under load, the shocks are piviting forward and back as well as up and down vs a shock that is perpendicular to the rear axle where all movement is straight up and down.
 
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