Turn the overdrive off with the OD button! Better have trans and radiator both checked!!! Possible coolant leaking into trans fluid, common on this vehicle and if that is the case it will destory your transmissio! .........Ok, just like greg said!
You would have to go into the transmission and disable the lock up solenoid, but then you are asking for more issues it that is disabled on these newer vehicles. Try the conditioner to see if it helps with the washboard effect, if your just trying to get rid of that.