Having problem with the up shifting into the 4th. high range .It will shift up at the marked speedo ranges 15 first- 28 second 58 third to 4th,but will not go into 4th at any other speed when you let up ont he pedal for normal 4th range driving- seems to be a vacum switch with 3 hoses on top of the engine a 4thport blocked with a screw. One hose goes down to the side of the tranny for shifting others go to various vacum ports IT was driven from Florida to Pa. by shifting manually L-S-to Drive Otherwise it stayed in 4th range at all times I reversed lines at switch on top of engine which gave me the proper shifting except for the 4th range. Could I have a faullty plastic vacum switch or the port that is blocked with screw go to something. Also tryed adjusting throttle linkage to no avail. ANY IDEAS --Thanks DON at DVW