Automatic transmission stalls between 2nd and 3rd gear

I have a 4.0 V6 2000 Ford Ranger XLT 4x4. The transmission, which is automatic, is having trouble after the installation of a new engine (for more on that, see previous discussion-- “2000 Ford Ranger with electrical, engine issues”).



The nature of the trouble began with two check engine codes. I forget the number, but one meant it “had no second gear” and the other meant it was having issues shifting from 3rd to 4th – which makes sense to me because it thought there was no 2nd.



Ford dealer used a special wrench to line up something or other between the engine and transmission – camshaft, driveshaft, I can’t remember exactly. He replaced a sensor and a gasket it had blown on the transmission – which he said that gasket never blows.



Anyhow, he thought he had it fixed. But he test drove on a four lane. When I drive in town (red lights, frequest stopping)…it still has trouble shifting from 2nd to 3rd. Instead of shifting, the rpms shoot way up, it doesn’t go anywhere, and I have to let off the gas and try it again before it will shift and get along little doggie like it should.



I called Ford, they said to use the shifter to shift it manually. This seems to work, so there’s hope for it yet. Any thoughts on what the problem could be?