Kgrove,
IMO there is a 95% chance that your rear AHC globes (accumulators) are shot. 5% chance that the globes are ok and it is something else (shock body).
Neutral pressure is related to ride height and load but not really to globe health.
When the globes are shot the symptoms are precisely as you describe and there are no other normal reasons that have the same result.
It works like this…
1) Bump hits the tire
2) Tire flexes, absorbs a little shock, passes the rest through to the hydraulic fluid
3) Hydraulic fluid carries the shock to the damping valve body at whichever corner we are talking about
4) Hydraulic fluid in the damping valve body is connected to the AHC accumulator globe via the damping valves*
5) The AHC accumulate globe diaphragm compresses and rebounds to absorb the shock.
6) If pressure is too high for the AHC accumulator globe to handle then *after* the globe is fully compressed an over-pressure valve opens in the valve body to release the excess (~1500 PSI IIRC) pressure back to the tank.
So: if the ride is harsh on small bumps but ok over big bumps what is very likely happening is that:
a) on small bumps the AHC accumulator globes are unable to absorb the shock (little gas pressure left) and the bump is too small to open the over-pressure valve so your tires are the only thing in the system with any flex. Result - you can count every piece of gravel in your drive
b) on large bumps the AHC accumulator globes are unable to absorb the shock (little gas pressure left) but it does not matter because the movement is so large it opens the release valve. Result - since the valve is open the springs and damping valve are free to act and the truck floats. Note that if the globes are 100% done… zero flex…then pretty much any bump will cause overpressure so the truck will have a 1970s Cadillac ride (float and bounce)
Since this started after you hooked up a boat what likely happened is that the old rubber could not handle the strain and lost most of its remaining pressure.
The easy way to check this is to put the back of the truck on blocks, remove one of the globes, and look down the throat. When you take it off if you get a few tablespoons of fluid then its probably fine. If you get a pint or two then you know its shot…which you can confirm by looking into the throat. If the top of the diaphragm is pressing the bottom of the throat area (about an inch down) then pressure may be low but still usable (and of course that diaphragm pressure prevents it from holding much fluid). If it is not then pitch it and get a new one (the weak diaphragm allows the globe to fill up with a lot of fluid).
My rears went before the fronts and I had ~10 gradations high-low. If all four are gone then it will be lower, like 6-7. With new ones you'll see 13-14. Replacing the globes is trivially easy BTW.
The alternate (unlikely given your story) would be a bad shock body. The AHC globes are a wear item. The shock bodies are not. That would be much more of a pain to check and to repair also.
Best,
Jonathan
PS: I have not been on the forum for a while (work) so email me if I don't respond.
jonathan@turnerclan.us