Re: Transmission issue help :(
Sounds like the converter is trying to find its "lockup" speed. That is the speed at which the converter is no longer a fluid coupling but a direct mechanical coupling. I believe that is controlled by a solenoid. It could also be that it is not going into overdrive and that is also controlled by a solenoid.
2003 ranger XL, reg cab, 2.3L, auto, 2wd. 115k miles