What you can try first if one is available is to update the transmission control module software. Once the software is downloaded have the adaptation reset back to zero and have them do an adaptive test drive to make sure transmission is fully adapted. Here is a description about the transmission adaptation from Volvo.
DESCRIPTION: The AW55-50 gearbox relies on adaptive data to properly adjust its shift pressure. This data is collected and memorized by the TCM and then used to adjust shift feel/quality. If the adaptation is not complete, it may result in: - Shift Flare: Engine RPM increases during a shift. This symptom often feels like the car has temporarily lost drive or the transmission is slipping. It is usually the 2-3 upshift that flares the most.
- Harsh Down Shifts: Harshness felt during a coast-down shift (zero throttle downshift).
- Harsh Garage Shifts: Harshness when shifting P-D, N-D, P-R, or N-R while at a standstill.
If this does not improve your condition then compare prices for the valve body vs. Replacing the transmission? With 80,000 miles you may be better off replacing the whole thing if you plan on holding on to your vehicle for a while. The reason I recommend the whole transmission is because if the valve body is failing because of a bad solenoid then there is something else going on with the transmission internally and is not really showing up yet. A few times I have seen the valve body replaced only for the transmission to completely fail a year later? I hope this helps and let me know if you have any other questions?