More car trouble

[packerbacker]

I've been having a hard time accelerating up to 60 mph or more. It accelerates fine before that but afterit gets to 45 mph my car seems to struggle to go faster. It also makes a humming sound when I go 60 mph. What could this be guys? I already had a transmission line replaced back in July that was leaking transmission fluid. I got that replaced and all of a sudden the last few days this problem popped up.