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Truck Air bags in Rear Suspension

I’ve got a 1997 GMC 2500 truck, 6.5 liter diesel, 4wd. In our area water hauling is very common. Most people with this size truck have 325 gallon water hauling tanks. This particular truck has rear air bags. A friend of mine has a Dodge 2500 (diesel) equipped with rear air bags that he has inflated to 60 PSI. He has a 500 gallon water tank and weight of the tank when full is 4305 pounds. He says the truck carries that weight fine and the bed of the truck only goes down an inch after he fills that tank. This is obviously overloaded. The 425 gallon tank weighs 3637 pounds and the 325 gallon tank weighs 2791. The 325 gallon tank is not a problem but I’m concerned about the effects of overloading the truck with the 500 gallon tank. Will the air bags be adequate for this? Will overloading have a negative effect on the automatic transmission and driveline? I’m not sure what brand the air bags are but saw online some say they can carry 5000 pounds.

The limiting factor will be the tires and wheels. If you have 8 lug wheels, full-floating rear wheel bearings, and load range “E” tires inflated to 65 psi and keep it below 50 mph, you should be alright…I would inflate the airbags only enough to prevent bottoming of the suspension. Let the trucks normal springs do most of the work…

The limiting factor will be the tires and wheels. If you have 8 lug wheels, full-floating rear wheel bearings, and load range “E” tires inflated to 65 psi and keep it below 50 mph, you should be alright…I would inflate the airbags only enough to prevent bottoming of the suspension. Let the trucks normal springs do most of the work…

Yes, I have 8 lug wheels and new load range E tires. The PSI recommendations for the truck are 80psi in the rear and 60psi in the front. How do you tell if you have full floating rear wheel bearings? I only have 5-6 miles to carry the water and 50 mph is about what I normally do on this road. The truck looks like it has been used to carry a camper in the past and apparently had a fifth wheel hitch attached to the bed at some time.

You undoubtedly have “full floating” axles. These can be identified by the small circle of bolts that retain the axle in the hub in the center of the rear wheels…If the tires are rated to take 80psi, then that’s what to use. Braking will be compromised, so give yourself extra room to stop. Get the “feel” of driving a heavily loaded truck…

When NOT in the overloaded condition, I would reduce the air in both the tires and air-springs to nominal levels in order to normalize the ride…

Thanks for the advice. I’ll check to see if they are full floating bearings. I’ve been hauling water with my 87 Toyota pickup for years (150 gallons), and it is slightly overloaded, so I’m pretty used to driving a heavy pickup.

You should check the owners manual for a good guide line on what the truck can handle. Most pickups have a weight distribution chart in the manual for mounting campers or fifth wheels. You might be able to just run overload shocks or add a leaf springs. If your not driving that far or that fast and over the same road it maybe cheaper to try something other than airbags.

Thanks for the advice. The truck came with air bags already installed. I did check and found that the rear wheel bearings are fully floating bearings. Someone else advised me to not drive in overdrive. Taking the automatic transmission out of overdrive would reduce the chance of overheating. Hauling 500 gallons of water would be about once every four or five days and only about 6 miles.