6 months ago i had to replace my original transmission, about a month ago everytime i get up around 55 the trans doesnt want to shift back down, by the time i am at 65 it is up to around 3400 RPM's, its not making any wierd noise or anything, if you werent looking at the rpms you wouldnt know there was a problem, is it ok to drive like this?? i'm not a very knowlegable car person so any help would be greatly appreciated!!! Thanks a lot!!!

Sounds like its not shifting into OD, when it goes to OD it has the engine an trans. turning on a 1 to 1 ratio , so the RPM's should drop back down,, I dont know what kinda warranty , or how long it was for . But I would dig up the paper work an take it back, kinda sounds like the OD band fried, Your fuel mileage is going to drop cause of this. plus wear the engine quite a bit more . An your tranny is going to run hotter causing futher problems. . In a nutshell its not good !!!!!!