Sometime the check balls or solenoid gets gummed up with varnish & dirt from heat build ups etc. Get the transmission scanned for fault codes.
This will help clean things up. Just add a can to the transmission and drive for about 500 miles and see if the harsh shift goes smoother.
Trans Tune - Sea Foam Sales Company
I would then switch up to Dexron VI (6) and I also used the transgo spring and spacer shift kit into accumulator body which is easy to install once the pan is dropped.
That solved my P1811 transmission code (long adapt shift problem) without having to remove or change out the solenoid at valve body.
I used 1000 grit Emory cloth in the accumulator bores to clean them up and get em smooth. The instructions that come with the TransGo Kit explains well the procedure.
Here is the photo from my shift kit install. This really firms up the shifts and eliminates the need in most cases to remove & replace the pressure & shift solenoids.