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IF the transmission has the correct level (based on the fluid temperature) and sometimes works right other times not, I would think you MIGHT need to have the filter changed with adding the amount of new fluid matching what you removed. IF that doesn't fix this intermittent shifting, I would think the conductor plate replacement. IF your good with tools and can access the bottom of the transmission, you can do it DIY. There is a .pdf here in the document collection to assist you. U tube has vids also. Before you do the filter/new fluid or conductor plate, do a lot of reading/vid watching. Good luck!
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