shift problem on 2001 GMC Sierra 2500 HD

position indicator light works sporadic on steering column, sometimes works fine. When it don't, the tranny stays in 2nd gear & wont change upon takeoff. I have been told to replace the neutral saftey switch, but I dont think that is the problem. Is there a switch on the column that senses gear lever position?

Asked by for the 2001 GMC Sierra 2500 HD
no that switch on the side of trans is it , most likely the problem follow instructions when replacing