90 MM 2.4 oil pump noise?

Started getting a strange sound from engine that almosed sounded like something rubbing but seemed to be a little slower pace than the camshaft would be turning. With a stethoscope it seemed to be behind the lower left plastic cover. As best as I can tell from the diagram that the area is in the location of the lower left silence shaft.
Question: Could the silence shat make a rubbing sound is it more likely the oil pump? The diagram I have seems to show the shaft going through the pump but don't know for sure. Any ideas of where to look first?
Thanks in advance...

The shaft is driven from one of the internal pump gears. Hard to spot but have you detected a drop in oil pressure? A balance shaft bearing may be on the way out or has actually already failed. The balance shafts are a weak point in Mitsubishi engines as the shafts rpms are way higher than the crank and cam. It can sound like a 'rumbling' when a shaft bearing fails. The shaft failing on the pump side is bad news as it tends to cause minute gear misalignment and float and then abnormal wear in the pump housing can occur.

Thank Geezer101
I'll look into the bearing first and check the pump specs. I don't have a warning light on but will pressure level first.