I have a 1997 1500 Silverado z71, my 2HI light never is on. When i press the 4HI button in any gear nothing happens, I can only use the 4LO but i have to put it in neutral for it to engage. and both 4HI and 4LO lights turn on. Today i had it in 4LO and it went back to 2HI and the light finally came on, then the 4Hi light was flickering. then every time i put it in neutral and pressed the 4LO button it went back to 2HI. it took me about 10 Minutes to get it back into 4LO. Does anyone know what the problem is?