Hang an accurate pressure gauge on the governor port and drive it - when you come to a stop the governor pressure must be less than 1.5 lbs., if it is you have an issue elsewhere in the valve body. Make sure you use a lower pressure gauge - 0- 60 or 0 a 80 as a high pressure gauge has a higher margin of error and you may not see a few pounds - and that will cause it not to downshift.