Transmission quit pulling when was going down road with no prevoous issues

What is your question?

Transmission tries pull for just a moment,then kicks back to no gears.Can hear it attempt to wanta go in gear, but doesnt.Had no issues ever was going down road ,tried to die ,then all gears went out,have checked all fuses..Did havd a power steering hose leaking,replaced that ,but still nothing.There's sensor with a vacuum plug,right beside it..toward back of tranny.What sensor would that be.Computer showed evap problem .

What makes this problem better or worse?

When take battery unhooked and hook back up,it tries to move but only for monent

How long has your 2000 Chevrolet Silverado 1500 had this problem?

Happened just out of the blue