A:AnswerThe Brother MFC7860DW machine works with the Brother DR420 Drum Unit. If you continue to have issues, our Brother Customer Support Team is available to assist you direct: www.brother-usa.com/brother-support
A:AnswerThe toner cartridge should be a separate unit and the drum is it's own entity.. In this case, I believe the toner cartridge sits on top of the drum assembly. The drum unit is only good for a few thousand copies and becomes dirty,, It must either be repaired or replaced.. Toner cartridges can run out of toner at any time depending on how much printing is being done.