i was getting this grinding noise at different speeds and rpms. mostly while accelerating but occasionaly while slowing down. the fluid was black and watery, so i changed it and the noise got better. but wheni put it into 4wdhi it gets reall really bad. sounds like the entire driveline is dry. and it doesnt kick out when i swtich back to awd. until i back up a few feet i was told it could be the tcase pump and the gears inside. i really hope not. any ideas?