These either seem to be bulletproof or fail, with little middleground. But, in typical Ford fashion, they give you plenty of warning, and will get you home almost always.
My 89 had no overdrive when I bought it. The torque converter clutch would lock, but it would never shift to 4th.
A $100 trans swap for another used one cured it and this one works fine. These are easy to find used, and easy, I am told, to rebuild, except for the front pump alignment, and the fact that they have more changes from year to year than any trans I have ever studied.
As a minimum, I would try changing the filter and fluid, and make sure the shift lever linkage and kickdown linkages were properly adjusted.