You have a 3-4 solenoid and a lock up solenoid. If you have lost 3rd and lock up you would have 2 bad solenoids. Not likely.
First thing that will cause this is 1 quart or more low on fluid.
Then plugged filter.
A bad pressure solenoid.
A filthy pan allowing junk into the valve body and hanging up valves.
Could be a worn out pump also. A pressure test wouldn't hurt. You can get a pressure gauge for about $20.00.
This is where I would look first.
If all that checks okay then you've likely lost 3rd gear and need a rebuild.
Rich
Sunday, June 7th, 2020 AT 9:10 PM