Del sol with M/T D16Y7 makes a humming noise while driving but only while in 2nd gear And very lightly in 3rd gear Does not make the noise When it is parked reved up to the RPM that it would be at in those gears with the clutch pressed in

 

Probably a bad counter shaft bearing. Pretty common in the d-series trans. It's not staked into the case and tends to wear out.

I think I got a full set of bearings from gearspeed racing when I replaced mine.