Plymouth Repair: transmission shifting problem, plymouth voyager, 1995 plymouth voyager

Question
I have a 1995 Plymouth Voyager.  In the last year, I've had 2 transmissions installed and the same problem keeps returning within a few months of the installation.
The engine starts immediately, I let it warm up for several minutes, then drive.  It will shift into 2nd gear, the RPMs get up to 4000 as I approach 45 mph, but it refuses to shift into 3rd.  I pull over, turn off the engine, wait a moment, and turn it back on whereupon I can drive and it shifts properly.
Any suggestions?  Thanks for your help.

Answer
Hello Chariene
this is not the tranny . thire is a sep. compuiter for the tranny . it is why when you shut your car off and restart it shifts ok . Take it back to the tranny shop and tell them u want a new tranny compuiter . this will end your problems . and get a refund for the troulble this tranny shop as put you threw . good luck to u hun pete