[T3] Auto shift issue

[Tim Keohane]

My T3 is shifting (automatic) from 2nd to 3rd at 55 mph. It seems like it was at 45 mph in april. It has been sitting for 3 months and upon re-introduction to the road it just started this. The shift from 1st to 2nd is at 20-22 mph. The shift is very positive (solid engagement) and that we must run it up to 55 to get it to shift into 3rd. It will stay/cruse in 3rd unless/until the speed drops to 45 mph, then it down shifts to 2nd. It seem like it's about 10 mph to high. 
Bently suggestions are the next step: checking pressure 
							        verifying that the vacuum modulator/canister is the proper one. 
Does anyone know the thread size for the test ports. ( I will make 2 pressure testers)
Does anyone here have any thoughts??
I have changed the fluids and cleaned the screen.
Thanks
Tim
73 T3 auto