Hello.I have a 93 w250 that has been sitting for years and was left in 4low.It will not shift out of low,but the front axle disengages. It has good vacuum at one of the lines at the actuator on the transfer case. I changed the actuator and is still is stuck in low. Any ideas what could wrong. I should have said shifter goes forward and the front axle disengages(it's vacuum operated) but the transfer case stays in low and the light on the dash stays on.