Can you describe this "little noise"? The things that can stop it from increasing speed and/or RPM are the limiters such as 4wd, reverse, seat belt..ect. The main limiter is around 7700 RPM and that's well past 45 in high range..normally. Other things are low fuel pressure or volume which can be a bad pump, stuck tank check valve, plugged fuel filter..water in the tank. Low coil power of low system power from a bad connection battery.. ect. The clutches can limit some speed if binding but won't stop the RPMs from increasing to the upper limiter. Of course there is the old valve timing problem some have but if that were the case it would run like hell all the way down and NOT correct by playing with the throttle.