Thanks for the replies thus far gang!. The 5er/hitch isn't the problem. It's just the truck's susp when going over bumps. Not sure if there is a gap between the overload brackets and aux springs and if there is and going over bumps, the aux spring thus gets engaged briefly for just that quick second to quickly enforce the whole susp back down which results in the "bag" I'm trying to describe. This is my 1st dually ever as I've always had SRW and for past 20 years short boxes. On my '03 F250, I installed Timbrens and had very good results and struck squatted about 2" as well. Over time, the factory springs got weak enough that the Timbrens were pretty much touching the axle full time. That in itself was starting to make for a rough ride empty. Spoke w/Timbren and they sent me a new set (presumably shorter), but got rid of truck after camping season was over.
After the '03 F250 (which I ordered BTW w/ camping/tow pkgs), I bought off the lot a '15 F350 SRW. While it had factory overload springs and tow pkg, no camper/5th wheel prep pkg. No rear sway bar, so figured I'd try Torklift Stabiloads (upper and lower). With both installed, the uppers were hitting the aux spring full time while the lowers were NOT engaged. Rough ride empty. Towing 1st 5er (pin wt of 1900), ride was still rough w/both. With just the uppers, I felt truck squatted too much. So I cut down/off a large portion of the uppers in an attempt to create a gap between them and aux spring empty. Cut darn near 1/2 of them and got a lil gap, so unloaded ride wasn't as bad, but still pretty rough w/ 5er. At this point in time, we sold the 1st 5er and got current one w/ a pin of 3700. Removed the uppers and tried just the lowers and ended up w/ the factory brackets hitting the aux spring w/ 5er on. Ride was vastly improved and handling was very good.
I didn't want to upgrade to a dually or for that matter another truck so soon after getting the '15 (purchased in Dec of '14) as I really like the truck and had it set up nicely. But as were planning our vaykay for this summer, we are heading south during the height of it and although I was over on truck GVW, really didn't bother me on that. The tires though IMO the weak spot. Already over w/o anyone in truck, so add in few hundred extra pounds, heat of just plain rotation, much higher ambient/outside temp, much higher road temp, all this combined was putting a pit in my stomach. If staying say north of a line from DC, no problem, but further south was bothering me on the tires. Would I have had problems/been alright? Perhaps. Many probly do tow w/ same kind of senerio. I myself just couldn't do it. So come along the dually.
Being a dually, it has a stiffer susp to begin with. If on the '15 and the aux springs were engaged w/ 3700#, the ride was pretty good w/ just the lower Stabiloads. Now I don't think/recall (Geesh I hate that I didn't pay attention last time we were hooked up.....darn CRS! LOL ) that the aux springs are engaged so have a gap between them. If I install the removed upper Stabiloads from the '15 that 2 things would happen. 1. Ride w/ 5er and bumps may be improved as the aux springs don't have a gap. 2. if no 5er attached and upper Stabiloads still hit the aux springs, unloaded ride will suffer. So I think there in lies my dilemma. I know Timbrens will limit how low the rear end drops and pretty much not allow the aux springs to engage and keep truck level. Air bags would pretty much do the same thing. If I don't see myself really putting a lot more weight on truck via pin, I "could" remove the aux spring altogether. No expert (hence my asking/seeking input), but sounds like the aux springs may be the root problem because I don't have any weight on them to work all the time.
Sorry for the very long post, but only real way to fully describe what's going on and how I arrived at this point and asking for assistance.
Thanks for all the advice and understanding.
