Chevrolet Repair: 1986 4x4 blazer, vacuum modulator, manifold vacuum

Question
just yesterday my truck started not to shift out of 1st. i have no idea whats goin on. you have any ideas on whats goin on or what i could do. any help would be great. thanx.
                  Dustin

Answer
Hello Dustin,
On the right side of the transmission, just above the pan lip, there should be a round gizmo with a vacuum hose attached to it.
First, make sure there is vacuum getting to it when the engine is running. That should be full manifold vacuum.
Then with a piece of hose, suck on that thing, and see if it holds vacuum. It should.
That is the vacuum modulator, and if it doesn't retract, it won't shift out of low.
Van