my 93 dodge dakota the transmision will not shift into overdrive but the other gears will i need to know what to change were it is located and what the part looks like

Yes, well, you actually need to have a diagnostic test performed to find out why what is happening is happening. No one here can figure that for you; you'll have to find a shop near you to help. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops There are no "common concerns" - your concern could be internal hydraulic or perhaps electric in nature. It may require tear down of your whole transmission -- or may not. Never know until testing is performed. Good luck!