Hello, Need a little brush up on the mechanics of the vacuum 2 speed shift on my 46 2 ton. It does not want to shift out of low range into high range at all almost like no vacuum going to the rear. Does not the control on the dash close one port and open another allow it to actuate the shift in the rear? I checked the lines going to the rear and they seem ok ,but don't want to start tearing into things until someone can refresh my memory. Thanks for any input, Jim
