no 3rd gear or OD

[Turboman]

My 87 GN has developed a sudden shift problem.After downshifting out of OD to 2nd to pass a car my trans did not shift back into OD.It went back to 3rd gear but stayed there.After parking and letting car sit for 1.5 hours I drove car and trans would not even shift into 3rd no matter how I drove.Car has shift kit and new Vigilante lock-up converter.Any ideas would be helpful.Anybody know of a good transmission shop in Chicago suburbs?

 

[MeanBuicks]

Sounds as if some trash is being generated somewhere causing sticky shift valves.