Shakes or Wobbles problem
2000 Chevy Express V8 Two Wheel Drive Automatic 114785 miles

AT 45 TO 50 MPH I LET OF THE GAS AND SLOWLY PUT MY FOOT BACK ON THE GAS IT KICKS AND FILLS LIKE IT SKIPPING UNTIL I GO HEAVY ON THE GAS . IT ONLY DOSE THIS WHEN ITS GOING TO OVERDRIVE , IF I'AM OVERDRIVE AT AROUND 60 PLUS MPH IT DOSE NOY DO IT WHAT COULD CAUSE THIS ?

It could be overdrive clutch chatter or the lockup torque convertor. If you have access to a scan unit, you can monitor when your transmission is shifting and what gear you are in, or going into, when the shudder occurs. This will help narrow it down.