So I bought a 2008 trailblazer with a slipping tranny because I have a 2008 withabadmotor

What is your question?

Long story short I had a tranny taken from one 08 trailblazer to another that had a bad tranny. I assuming he didnt flush the lines and cooler on new one because it shifted fine first drive now it's not changing gears. Someone said if he didnt flush lines it could have screwed up new one. Anyway of saving it at this point