1993 Thunderbird transmission problems , transmission repair shops can't fix it

Took car to transmission shop when the car started to slip gears,  After car
warmed up, RPM'S would go way up as car slowed down, as long as you shift
into third gear the car was ok. They duplicated the same problem.  A month
later they thought they fixed the problem, got the car back and after driving 15-
20 minutes started to go up a little hill it started to repeat same shifting
problems again.  They have rebuilt the transmission twice, replaced throttle
body twice and replaced the governor.  They decided to get a new shell and
rebuild it, the the new throttle body had a hairline crack in it and they replaced
it again.  Now the car is slow shifting on takeoff and now I have loss of power.
The ebgine was running great when the car went to the shop 3 months ago,
now it seems to be worse.