Hi, I have a 2005 GMC Sierra, the indicator lights work on the 4wd selector switch, when I switch into 4HI the light indicates I am in 4HI but it seems like the transfer case is slipping?? I press on the throttle and I need a lot of throttle to get moving and if it moves it jumps.. any ideas what could be causing this? Bad transfer case? Bad encoder motor? Bad actuator? I have no clue.. any help is appreciated, thanks in advance!!