Yup as above.
Engine needs to be in fresh tune, New Iridium plugs, air filter, fuel filter, wires etc for electronic control transmission to be right as well.
No check engine lights too.
If you can get a transmission shop to do a scan with a good high end scanner it may find the dreaded P1811 long adapt shift code. Thats what i found when trans go hot and it got some harsh shifting going on.
I then put a can of Trans tune in to clear varnish from the valve body end.
Trans Tune | Sea Foam Sales Company
Harsh shifts went away, and drove then for 700 miles with the can of trans tune in.
Then I installed a trans go shift kit with springs & spacer into accumulator which is accessible once the trans pan is off. Used the new fluid-Dexron VI
(6) and all will be good again if ya got P1811...like I did.
Re scanned a few weeks later all is well no codes.
I did the shift kit install myself in about 1.5 hours to on road and re-filled.
TransGo | 4T65E: SK 4T65E
pics of my shift kit install makes sense as shift kit comes with good instruction, and then u can relate to pics from on bench.. Emory cloth to clean the bores is on bench too.
4T65-E Transmission Questions Help