1995 Chrysler New Yorker Shake/Shudder/Hard Shift

I have a 95 Chrysler New Yorker that I purchased the other day to replace my Jeep that died. (I miss it).

When I first purchased the vehicle, it had really bad vibration, road noise, and what sounds like a clunk when going over bumps.

After replacing all 4 tires, and ensuring the rims are true and free of cracks.I've eliminated most of the vibration and road noise.

However, it still has two things I need an opinion on. The first is the clunk I hear when going over bumps. When the tires were replaced, I noticed the front struts appeared to be bad. The boot was brittle and pushed up and I could see the piston of the strut. So I attribute the 'clunk' to possibly that. Thoughts?

The second, is a noticeable vibration when accelerating. It's sometimes accompanied by a hard downshift in the transmission. Mainly only happens at around 30-60mph. If I'm cruising on the highway at 70mph and go to accelerate to pass I don't notice it.

I went to three service centers and all of them told me since I don't know if/when the transmission was ever serviced, that it would do more harm to flush/fill it than it would to leave it alone. So I added a bottle of Slick 50 High Mileage Automatic Transmission Treatment and it helped just a bit. Not much, but I can notice a bit smoother shifting under load. The vibration and hard shift is still there though. Any thoughts?