Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If the fading down the page is not cured by drum replacement, not affected at all really, then you either have a problem with your toner cartridge (possibly damp toner, in need of shaking up, by removing the cartridge and shaking it swayingly some to break up clumps), or you have a power supply that can't support the needed voltages for the whole 1-page worth of printing activity.
At least, those are possible causes to look into.
OK Casey, thanks for letting me know. Get back to me about the Sharp machine at your convenience.