i have a 1989 fj62 and the the 4wd green light wont go off. the hubs are in free position and i transfer case is set to H2. around 55-60 mph it starts to humm a lot. i have pushed the switch to the off position and the light stays on. i'm pretty sure the 4 wheel drive is engaged. any suggestions on what i can check for to correct this problem. thanks.