RPM's
 

I have a 2003 civic with approx. 185,000 miles. approx 4 months ago the transmission went out and I replaced it with a transmission with 45,000 miles. It seems to work well. shifting and clutch sound and operate normally. However, the last couple months RPM's do not seem t drop when shifted into 5th gear. Does this sound like a transmission problem or ?.

all help is appreciated.