Can't seem to determine quadrature encoder resolution
Well, 400 counts per revolution generally refers to counts in terms of the four possible state combinations of the two outputs. If you just count pulses on one channel, you will get 100 pulses per revolution on a 400 count per revolution encoder. You need a quadrature counter to actually get all 400 counts. 100 pulses times a gear ratio of 30 is 3000 pulses per rev, which is in the ballpark of what you are seeing.