I have a 2003 Ranger 3.0L v6. Im assuming my transmission went out. The reveres gear has stopped moving the truck if i tap the gas continuously itll try to move but then just revs, like its at the very top of throttle. To drive it forward I have to put it down into 1st then shift accordingly into 2nd then into drive. If i don't let off the gas when shifting into Drive it'll just rev up but if i let off it shifts somewhat fine and seemingly into 4th. Idk what to do someone help. Could it be something to do with the transmission computer thing on the side of the transmission?

 

Welcome to the forum

Yes, trans needs to come out, you have a failed one-way clutch(sprag), or 2
No, not a computer thing or even valve body thing

The one-way clutch engages Reverse and Drive, no computer needed for that
When you manually shift to 1 then the Coast clutch can be used and start you moving forward, and you may be able to shift to D then and have it shift to other ratios(gears)

2003 3.0l Ranger will have a 5R44E automatic
You can used a 5R44E from a 2001-2008 3.0l 2WD, assuming 2WD not 4x4, that's a different transmission
Can't use a 2000 or older model

You can check at car-part.com
They look at local wrecking yards for used transmissions, don't worry about "sub-models", 2001 to 2008 5R44E from a 3.0l 2WD will work in your 2003 3.0l 2WD

Or do a full rebuild on yours, not just soft parts(clutches and bands), need one-way clutches(of course) and new pump, new valve body and OD drum