It sounds like you have a problem with the second to third shift solenoid. Here is a guide to help you remove the transmission pan so you can do the job:
https://www.2carpros.com/articles/how-to-service-an-automatic-transmission
Below are some guides to help you see what the job will be like. Also I have the transmission wiring diagram to help you see which solenoids needs replacement.
Let us know what happens and please upload pictures or videos of the problem.
Cheers, Ken
Images (Click to make bigger)
Sunday, December 10th, 2017 AT 4:14 PM