Overdrive light flashing

Hello,I'm Danny.

That sounds like you might have a transmission code stored in your truck.Using a scanner/code reader will give you the stored code(s).If you don't have access to one your local auto parts have a tool loaner program and can rent you one.Some places like AutoZone can retrieve the codes for you for free.Here is a tutorial showing what is involved:

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

If a code is stored and retrieved please get back to us with the code number and we can then help properly diagnose the problem.Hope this helps and thanks for using 2CarPros.
Danny-