I just bought a 2007 impala and when I step on the gas it bucks into first gear but after that it shifts good ?

It does not always buck only when i put my foot down a lil hard...My impala has 78xxx miles on it with traction control I think it's that because wen I take it off traction control It does nt buck as much. I hope It's not the tranny other than that it shifts perfect. Also I need an alignment so idk if that's why it's acting like that.