rear jounce bumper (bump stop) on 2000 Chrysler Town & Country

When I go over a bump, there is a loud thud (metal to metal?) in the rear of my 2000 T&C AWD. Sometimes it does it when I make a turn. The rear bump stops are worn out and I need help how to replace them. Thanks.

Asked by for the 2000 Chrysler Town & Country
I think you need shock absorbers. The bump stops are bolted in and you should be able to see that if you look.
I replaced the shocks, but it still does it. The bump stop is attached with a rectangular base with a built-in bolt. The whole plate has to turn to unscrew, but there's no way to get hold of it because it's too big for regular pliers. I tried tapping it counterclockwise to get it started so I can get it out with my hand. No luck. Is there a special tool? I've been working on this for a while. The only place to get the OEM bump stop is the dealer. The aftermarket ones are cheaper but I still need to get the plate off. Thanks for any suggestions.