My 1680 is dropping below 2450 rpms and causing the alarm to sound. I've replaced both filters, the lifter pump up on the side of the motor, and the electric pump down on the side of the machine. None of this has solved the problem. When it starts to alarm i can slide the throttle forward and the rpms come up and it runs like it is supposed to. I'm wondering if the the throttle linkage has moved and the combine cannot run up to full rpm. The rpms are around 2580 when at full throttle. It only drops below the 2450 when the machine is loaded and pulling a hill. Anyone have any suggestions?