Mazda 6 Service Manual: No.19 excessive shift shock on torque converter clutch (tcc)

No.18 excessive shift shock is felt when upshifting and downshifting

No.20 noise occurs at idle when vehicle is stopped in all positions/ranges

Other materials:

Mazda 6 Service Manual: Manual Transaxle Shift Pattern
  The shift pattern of the transaxle is conventional, as shown. Depress the clutch pedal all the way down while shifting; then release it slowly. Your vehicle is equipped with a device to prevent shifting to R (reverse) by mistake. Push the shift lever downward and shift to R.   ...

Mazda 6 Service Manual: Clutch cover inspection
1. Measure the wear of the diaphragm spring fingers. If not as specified, replace the clutch cover. Depth 0.6 mm {0.024 in} max. 2. Measure the flatness of the pressure plate with a straight edge and a feeler gauge. If not as specified, replace the clutch cover. Maximum ...