My 1998 Expedition OD is blinking and it misses 3rd gear (OD?) but, if I turn off OD the light stays blinking but it shifts twice and doesn't try to shift further but I'm running 40 mph at 2500 rpm.

In the last 3 years I have been ripped off twice by transmission shops! the first was in Michigan where I am originally from. I had it rebuilt before going to Miami but the tranny went out in Miami, I had it rebuilt there and they told me it needed new lines along with tranny cooler and converter, which I just had done in Michigan, and new exhaust because it also had an exhaust leak I asked about fixing...I picked the truck up to go back to Michigan (shop owner could not be found) the exhaust was worse than ever, the tranny cooler had bent fins and half way out of Florida a line blew where it had been kinked!
And now this!! I have more invested in Tranny rebuilds than the Expedition is worth

 

You need to get the codes read. The places that read codes free CANNOT read these codes. Without the codes all I can tell you is that something is wrong.

 

Sorry to hear... luckily transmission issues are easier to diagnose and fix compared correcting engine issues. Hopefully you get the code scanned and it's a relatively simple fix. One thing about these trucks is you can pickup a used transmission for around $500 or less. Do you know the name of the shop in Michigan you had it worked on at?

 

It's times like this that having the work done at a national chain is beneficial. Even if the work was done in Michigan, the shop in Florida would honor the warranty.