brother intellifax 2400 ml

this laser fax machine has been in my possession for about three years of relatively little use. The background has been getting progressively grayer and the text progressively lighter. I changed the toner last week and cleaned everything that was supposed to be cleaned according to the manual. The text is much better but the background is much darker and it is almost unusable. Brother told me that the drum might be bad, but for less than the price of the drum, I could get a new machine. My feeling is that something I didn't clean is the problem. Any
suggestions?