O/D off

Yes, you should have a small button or switch that controls whether you want overdrive or not. it should be on the shift handle or dash. Can you check it out and let me know?

Cheers, Ken

It is on the gear shifter. it is an automatic.

Does the light respond to the switch or is the light blinking or you cant switch the OD on? sorry for the twenty questions just need to know :)

Cheers, Ken

The 20 questions are absolutely fine. I actually have so many questions because there's so many issues wrong with the Jeep. If you don't mind I'm just going to ask you all of them but when I press the button a light comes on that says O/d off. Also my Jeep is smoking, I've changed the spark plugs, wires, and valve cover gaskets. But it's still smoking, but NOT overheating.

Okay that is better, lets handle one problem at a time you will need to start new threads for the other issues. We are after the overdrive problem first.

It sounds like you have input speed sensor for the transmission that is out but to be sure lets run the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back

Cheers, Ken