If worse comes to worse and i mean there are no other alternatives. Change the the tranny fluid and add an additive to soften the seals in the valves. Run the car and see if this makes a difference. If it does drive for a while. Get it to operating temp and then drain the tranny fluid again. If I recall correctly the filter can't be removed unless you open up the tranny itself. So try this first. the clean fluid will bring the viscosity up. Hope this helps.
Weebs
