1994 galant with 97 trans having problem!!

hello guys, i got a 94 galant es which i had problems with the tranny, so i got a 97 tranny in perfect condition which i tested in the car that it came from and it ran fine, but until i install that tranny in my car. now my car has the 97 tranny but the car run slower and it's not changin gear. i did install the torque converter that came with the 97 tranny. the car runs slower doesn't change gear and it feels like is slipping when i give it gas. i try checking the tranny oil but i got hear so many different ways on checking the trans oil, that i don't know which is the right way to check the oil for the tranny. can anyone give me any suggestions on this problems. thanx for the space.