I have a 89 dodge dakota v6 automatic trans. it has push button overdrive but no matter how much i push the button it will not shift into overdrive what could be wrong?

Is there a light on the dash by the gauges that indicates "O/D off"? And do you mean it will not shift up in to O/D and stays in 3rd gear? I think we can figure this out. The O/D on/off system is an electrically controlled thing, start with fuse and let's go from there.

yeah there is a light and it does come and yes it stay in 3rd gear

And i looked in the book and theres no fuse for that and all the other fuses r good

Very complex system. the engine computed decided when to shift into 4th. it send a ground through he circuit board inside the od switch. the wire then goes to the trans and then the 4th gear shift solenoid is energized sending fluid pressure into the compounder and shifting into 4th. the engine computer looks at tps signal speed signal coolant temp and the map sensor for info in when a shift is appropriate. and still with knowing all this I still haven't been able to get mine to shift into 4th gear either. id start by supplying a ground to the pin on the trans for the 4th gear sel. if doing this gets the trans to shift into 4th then compounder "4th gear" and solenoid are good. and your trouble is not in the trans.