5r110 shifting issues

[ihtrucktech]

I think my trusty torque shift is giving up on me. It seems to go through 1-4 fine nit occasionally under load when it locks up in overdrive it surges. (The engine free revs for a split second). Could it be my torque converter? Last if it is cooked what is the best way to go for performance upgrades for it? All this is for the truck in sig.... thanks