Does anyone have the procedure for adjusting the gear reduction motor drive units on the side of the gantry for the Y axis?

My Y axis is extra loud lately and I noticed that in one direction the left side lags behind maybe 1/2" then seems to catch up. Adjusting the three bolts and slightly adjusting the motor units seems to change the noise level and some of the binding, but I can't get it right and the lag seems to continue.