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Rrliljedahl's avatar
Rrliljedahl
Explorer
Mar 15, 2016

Over weight truck camper suspension upgrade needed

I need some advice.
Mounted a custom flatbed camper to my truck and realized that it was squatting in the rear.
GMC Sierra 3500 2007 Classic LBZ Duramax Diesel with 6 speed Allison Transmission.
Body is like 2006. There were 2 body styles in 2007. This is the older style.
Single rear wheel.
Tires size was increased from roughly a 32 inch to roughly 35 inch.
Truck was regeared from 3.73 to 4.52 to compensate for bigger tires and weight of the camper.
Rear Firestone Ride-Rite 4800 pound air bags were added and do lift the camper up when inflated.
On a CAT scale, camper/truck with a full 32 gallons of diesel and 50 gallons of fresh water weighed 12,100 pounds with factory GVWR 9900 pounds
Front tires are carrying 2500 pounds each (series E rated at 3850 pounds) with factory GAWR FF 4800 pounds
Rear tires are carrying 3400 pounds each (series E rated at 3850 pounds) with factory GAWR RR 6500 pounds
Axle is rated for 10,000 pounds.
Cognitio front steering upgrade has been performed.

I know I am significantly overweight but the plan is for the camper to stay mounted to this truck. So far, truck did fine on the interstate driving from Denver to Salt Lake with no porpoising or rocking with the air bags inflated. However, when on rut filled roads looking for a spot to do some dry camping, the camper was rocking quite a bit back and forth.

Without the airbags inflated, the rear sorings are pretty flat with only about 1 inch between the tires and the flatbed. With the air bags inflated, I have about 4 inches between tire and flatbed.

Talked with truck suspension shop and they recommended a factory gmc "heavy duty" rear leaf spring replacement good for 4000 per side. They also suggested I might want to consider upgrading the shocks.

I would post some pics but do not know how.

Short of replacing the truck, what would you recommendable for additional suspension upgrade to get the sagging rear end of my truck back up so that it rides better when off pavement?

Thanks.
  • What camper are you hauling? I would add stable loads (stopped the porpoising) but the spring upgrade is sound advice from what I've seen.

    We have a 2006 Silverado DRW and when all of the containers are filled with diesel and fresh water we run about 14,300# and it still rides high in the back, I don't put air in the bags until the camper is on so must be the added wheels.

    Would not want to try and haul the 1150 with a single rear wheel so wondering what your camper alone weighs.

    Bill
  • Tires are likely the biggest problem. You can either replace the srw with a drw axle wheels and tires, or go to 19.5s. I'd also upgraded stocks if you haven't.

    After that consider a spring upgrade and brake upgrade.
  • If you plan to leave the camper on all the time, the heavier stock springs sound like the way to go. Are your air bags connected to each other with an airline? If they are, it will work against you on sway. They need to be separately valved. Also, they will fail, eventually, so have a "plan B" ready. The heavier springs would help that by taking some of the load off the airbags, reducing the effect of losing one on a trip.

    I don't know all the ratings and safety margins built into axles, wheels and tires, but I run at about 10,000# on an '04 Silverado 2500HD with a set of Supersprings. Basically, that's the same truck. I'm okay with it, but if I were at 12,000#, I would want heavier springs, and higher-rated wheels and tires.

    JMHO!
  • Ours is the 06...see my sig. I don`t see anything about a sway bar, I would recommend that and definitely upgrade the shocks, and I agree with Jimnlin about the 19.5s that was by far my best upgrade. It will still rock side to side on rough roads at slow speed when the potholes are perfectly spaced....
  • Ours is a 06 GMC 3500 DRW. Added flatbed, has the 8.1 W/Allison. With camper on my rocking back and forth was all but stopped by adding the rear sway bar, ordered it on line, short install time and the suspension is all still factory. Photo in my (profile).
  • Some points here on your upgrades.

    Although you have 3800 lb rated tires did you also upgrade the lower rated OEM wheels ?? This is one area 19.5" wheels and tires shines for carrying heavy truck campers.

    Air bags with high inflation pressure can add to your trucks sway issues. The truck suspension shop has the right idea about heavier rear spring sets.

    And your trucks axles load numbers don't add up. Scale weights gives us a number in 20 lb increments. Your 5000 lb front and 6800 rear axle numbers must be a estimate..... which add up to 11800 ....not 12100 lbs.
    I would want to see my trucks actual scaled separate front and rear axle load numbers. That way you know which components may be severally overloaded and the best fix.
  • Rrliljedahl wrote:

    Short of replacing the truck, what would you recommendable for additional suspension upgrade to get the sagging rear end of my truck back up so that it rides better when off pavement?

    Thanks.

    I would suggest Super Springs...don't think you want an anti-sway bar for off road travel...unless you can easily disconnect.
  • Short of inventing an anti-gravity powered hover truck, you will not be able to eliminate the rocking on "rut filled" roads. It is a function of the road.

    A heavier factory-style spring pack is the "right" way to go, if there is such a thing as a right way in this situation. Anything else is an add-on and puts stress where it's not necessarily designed to go.

    Maybe a big rear sway bar to mitigate the rocking some.