99 ranger pulse vacuum motor/generator?

Ive recently been working on my truck, 99 4x4 ranger, well the 4x4 stop working now i think i found the problem, what ever this thing is, motor/generator/acuator, it is not working properly. anyone know where to buy this at. it has numbers on it. they are on the top: pa66-gf33. on the side of it it has : f37a-9e441-aa 909d0507. please someone HELP!!!!!!!!