I didn't have any luck with my local driveline specialty shop,here in Iowa. I remembered someone re-building a 2-speed vac-operated system back in the '80's. It looked simple enough,so I removed the 3, 9/16" bolts (on my '55 6500 T.F.). I noticed that the vacuum lines were dis-connected for a reason. the "pancake" had a hole DRILLED through the top of it,with what appeared to be a coat hanger attached to the rod that actuates the 2-speed! I removed all the screws attaching the "pancake" together,since the diaphram is sandwiched between the 2 pieces. AS I suspected,it was dry-rotted badly.I cleaned the mating surfaces with gasoline,as well as 2 layers of truck (20") inner-tube.I then cut the inner tube to fit the outline of the pancake,then I cut one duplicate,to form a double layer.I then "Permatexed" the mating-surfaces on the "pancake, and put the two halves together,to set-up over-night. The next day,I used an awl,to form the holes,so I could screw the "pancake" back together. I used J.B. weld to block-off the hole drilled for the clothes-hanger. I tightened down the 3,9/16" bolts,started "Mater" up,and WOW!! no vac.leak! Then I took "her" out on the road...Low and High side...Works Great!! Mine didn't have a rotary valve. the rod is attached directly to the diaphram. The two hoses are on opposite sides of the rod.Let air in chamber"1" (button "down"),you're on the "low' side. Let the air in chamber#2,(button "up"),you're on the "high" side. I had fun rebuilding this thing, and it's really easy to do! Hope this helps.
