I have a gmt400 and I’m currently having transmission problems I drive for a bit and my truck will shift fine 1-2 is sort of rough but 2-3 will take a while to disengage from 2nd then engage into 3 it will do the same thing as I down shift from 3-2 and afterwards my truck jumps into limp mode does anyone know what is going on is it’s a leak or could it be a bad solenoid I have no check engine light and I can’t get my hands on a obd1 scanner so I’m absolutely lost right now I also would like to know what transmissions I would be able to use so my truck will run smoothly.