Still having bucking in overdrive

I replaced plugs, wires and coils and it runs smooth except when overdrive is on, it has plenty of power and shifts great with no slipping, transmission fluid is very clean and it has a new filter.
when it goes into overdrive the tach is jumping between 1500 and 2000
ad the car******/bucks, does not feel like a misfire at all.
if I give I a little gas it comes out of overdrive ad goes smooth until it engages again,
is there a way to disable the overdrive without causing a check engine light?
i tried unplugging the solenoid from the transmission and the light goes on and there is no power like it is dragging in a high gear.
there must be a single wire I can cut to shut it off.