96 3.0L automatic Ranger slamming into gear from park

[98v70dad]

My 96 3.0L automatic Ranger is slamming into gear from park. It happens shiftng from park to drive and park to reverse. It doesn't happen all of the time and happens most often(and most likely) if the truck has been parked for a few weeks. Usually shifting the selector through all of the gears with my foot on the brake and revving the engine will get it to go but only with a big slam into gear. The truck has about 85,000 miles on it

The fluid level is full and was changed out a few years ago at about 50,000 miles but it was suctioned out and the filter wasn't replaced. Every couple of weeks I would suck out about 3.5 quarts and replace the same amount (mercon fluid). I did this over a period of about a month until I had removed/replaced about 9 quarts. I have checked for loose bolts in the selector on the steering column and that is all tight and good. I don't have any trouble codes or check engine light.

I've read that the valve body gasket and/or the solenoid pack could be bad. Is there something simplier that could be causing the problem? My guess is that its the valve body gasket but I'd appreciate other opinions since that's a cheap and relatively easy fix but definitely a big mess.

 

[98v70dad]

Also, my truck is a 2WD.