My 2001 Chevy Silverado does not have power in drive or revers it only has power in park an neutral what could be the problem only transportation need to find the result asap

The cable is not allowing it to go into these gears.more than likely a new cable is the resolution .

Possible reverse light switch. Or park/neutral safety switch. What side of the case are the wires coming from?

The best way is to take your time...,Set Emerg brake,start vehicle and put into neutral..Engage 4 wheel drive,look at your dash gauge area for 4 wheel drive light to come on..Put truck in reverse and release park brake..,Back up 10ft.slowly..Then put it in drive and pull up 10 ft.slowly then you should be in four wheel drive..

Sounds like the reverse band or servo has gone out. Transmission shop needed for a confirmation.

You probably have a battery problem - have it and the charging system checked.

that could be a bad, loose or misadjusted "neutral safety switch" .. in some the brake has to be applied before starting .. that would involve a brake safety switch ..

2 things come to mind off the bat plugged cat ir a fuel problem,pump,filter,regulator,

sounds like your trans linkage needs adjusting.