There's a member here who posted up a picture of his 2500HD towing 20,000+ lbs and he says he does it on a routine basis with no hiccups. I'd think that's more stressful on the trans, but who knows.

 

Mine has a LAME 2-3 shift. I'm sure I installed just the white spring for the 3rd accumulator but still I've had to add 80 psi shift pressure at WOT to make it even feel decent compared to the 1-2 and 3-4 shift. Its possible I have a direct clutch issue but I don't know. To me it would seem a firmer spring would make a firmer shift and a softer spring would make a softer shift. Accumulators are just shock adsorbers for the hydraulics of the transmission. They cushion the apply of the clutches so you don't get hard parts breaking shifts.