700r4 question

[85 K5]

cruising the neighborhood, 20 - 30 mph seems like at real light throttle the tranny shifting acts strange, as if it doesn't know which gear it wants. Say if I let off the throttle as it's trying to shift. Is this normal for this tranny or is there a servo or clutch problem? All other functions are normal in fact it works very well shifting, downshifting, etc. Goes into reverse quickly when cold and shift points are ok. Fluid is red and does not smell burnt, it gets a yearly service. It was rebuilt 25k miles ago with supposedly stronger parts and a shift kit. Any ideas?