And the Lucas oil stop slip solution, or Lubegard won't make a difference. It might actually make things worse depending on what's inside of it; your car would be the experiment. It definitely won't solve any transmission issue should it occur.
Change the transmission solenoid, my old car use to do the same exact thing. Installing a transmission cooler might benefit it for a while longer.
I didn't drain/refil because of horror stories lol.
Be prepared for a flashing d4 on your cluster.