98k1500

I HAVE A 1998 K1500 PICKUP IT HAS THE VORTEC 350 IN IT, THE QUESTION I HAVE IS- WHEN I AM DRIVING DOWN THE ROAD DOING AVERAGE SPEED IF YOU GET ON THE GAS TO KICK IT INTO PASSING GEAR AND THE RPM'S GO ABOVE 3000 IT SOUNDS LIKE I HAVE GEAR DRIVE ON THE ENGINE, IT DOES NOT DO IT WHEN THE VEHICLE IS IN PARK AND YOU REV IT UP TO 3000 RPM'S OR MORE, I HAVE ALREADY REPLACED THE IDLER PULLEY AND THE TENSIONER ASSEMBLY ALONG WITH THE BELT DOES ANYONE HAVE ANY IDEA WHAT THIS MIGHT BE, WOULD REALLY APPRECIATE ANY INFO. THANKS