moaning/groaning noise at 4500rpm

hey guys/gals,

i have a 98 talon NT or NA and have replaced my engine recently. ever since i got the new engine installed the car has been groaning at 4500rpm on the dot. it comes on and stops at 5000rpm. i have never heard this happen to any car. anyone have any ideas as to what it could be?

thanks

aaron

replaced the harmonic balancer and belts as well