1987 V30 Dual rear wheel axles?

[Turbo Dog]

Forgot to say...Thanks for all the input!

 

[Grit dog]

Maybe the best bang for the buck would be to move the rear axle back? Looks like you have room and it's a straight frame C&C truck, correct?
You also have options that are still suitable for light duty trucks, bolt on and go (not claiming how economical you could get one) for a heavier rated axle. AAM 11.8 and 12.0 axles used under new Ram Duallies would be acceptable, although they too changed the lug pattern, not 8x6.5 anymore on the recent years Ram duallies.
Given the occasional use with full load and presumably care taken, a 14bolt should still last a long time. It's working now and the way the load center is, is taking a disproportionate amount of load already.

 

[Turbo Dog]

I think I already have the stock axel overloaded. But I think it is working due to the fact that it only travels about 10 miles loaded.

 

[Grit dog]

With full or near full water, you absolutely have it overloaded, by 4klbs easily if full of water. But duty cycle and the health of the axle are on your side. Like you said, 10 miles, occasionally. Not 200 mi a day every day….

 

[Bextreme04]

I think I already have the stock axel overloaded. But I think it is working due to the fact that it only travels about 10 miles loaded.

I doubt that. The axle isn't the weak point there. The 14BFF C&C dually version has 3.5" axle tubes that are 1/2" thick. The gross axle weight rating for that axle is AT LEAST 8600lbs per GM. The part I'm worried about is the unboxed rear frame and the spring mounts. If the flat bed is heavy duty enough and well secured though, that likely isn't going to be an issue either. I bet you would get a lot of the lightness out of it and solve your actual problem by just putting some good quality airbags on the axle and spread the airbag load through the frame and flatbed.

 

[Turbo Dog]

The current load of the tank and 750 gallons of water is 6525 lbs even adding an approximate weight of 500 lbs for the flat bed would keep it well under the 8600 lbs. But once I fill the tank completely it will be 1000 gallons at 8,300 lbs plus the 300 lbs for the tank. I think the flat bed stiffens the frame by being attached with U bolts in the front and back.

Yesterday I picked up the usual 750 gallons and measured the sag at the back of the flat bed at 3.5" fully loaded. Seems like that amount of sag could be handled with air bags. But will they work without moving the axel back?