I have a 1996 Silverado I just bought. It was sitting for a few months and the previous owners had their dogs chained to the bumper and they chewed the wires for the 4wd. I reconnected the wires and the 4wd still doesn't engage. On the top end the 4wd button on the inside says 4wd is on but it's still not going into 4wd. Has anybody had this problem before and how can it be fixed? Thankk you.