Have a 2001 Ranger almost 230,000 miles never had tranny problems. Use it as a work truck but been out of work for about a month have not really been driving truck but before last Saturday been telling myself time to flush tranny but before I could do that noticed o/d light blinking and shifting funny. Got home let sit for a while no problem but drove it Monday and noticed shifting funny and o/d light blinking again but only cause i put foot in it a little. Also i do all my service work and is a true believer of Lucas products. I'm thinking taking it to auto part store to let them read the codes if any and also change filter and tranny fluid. But other than that never had a problem must admit it's been a while since last tranny flush

 

Welcome to the forum


2001 was transition year for the Ranger automatics
3.0l could have 4R44E(4-speed) or 5R44E(5-speed)

They are the same transmission, 5R has an electronic 2nd gear, so different computer firmware.

Flashing OD light means computer is using "limp mode" for shifting and operation.
"Limp home" mode, lol.

Yes, see if any codes are set and after WRITING THEM DOWN!!!!!!!!, reset the computer using the code reader.
"I think the code was.........." is worse than no code at all

Not all code readers can read transmission fault codes, so don't reset it if it doesn't see any codes, go to a transmission shop, and pay, if needed, for them to read the codes.

There, for sure, will be codes if OD light is flashing.
Code might not even be for transmission, engine sensors can cause computer to use limp mode, but CEL(check engine light) should be on if that was the case.
Does CEL work?
Does it come on with the key and then go off after engine starts?

Yes, changing fluid and filter is a good idea, but I would wait until after codes are read.
Could be you will want to pull the pan to change something.