22 LTD Sudden loud clunk felt in rear as I stopped

Besides the drop in mpg after engine replacement, yesterday (I had accelerated a bit as I sometimes do to make sure the turbos are working), I then eased off... no problem....approached a light..... and just as I came to a complete stop, I felt and heard a deep, heavy "CLUNK" in the rear, and felt what was liked someone tapped my rear end with their car.

43k miles, haven't towed anything yet, rarely offroad, and when I have, it's been mild and level. I received the new engine under warranty (though last engine was working fine) was installed last month. No problems since then except mileage. Great acceleration, rarely hesitating, but again, TERRIBLE gas mileage (lost 2mpg at least, and with city driving in normal mode anywhere from 8mpg to 13, with combined 50/50 only about 15). If I go in eco mode on flat freeway, it's about 19-20, but any average highway acceleration brings that down to 17.

Anyone else have this clunk happen? Only once so far yesterday on way home. (I also have an engine replacement thread, I'll post there too)

 

I had a similar experience just a few days ago...a loud clunk that felt like I had been rear-ended when I came to a stoplight.

Fortunately, it just a heavy tool box in the bed that I had forgotten to tie down. I wish your issue was that simple, but I doubt it.

I'd crawl under your truck and start grabbing and yanking on anything you can. Hopefully its just a loose suspension component.

 

I’ve gotten it before. Accelerated up a short hill to a stop light, coming out of a parking lot. Only happened once, so far. I think it confused the shifting sequence. Instead of the upshift it expected, a quick downshift was needed.

 

Good to know. I'll have the dealer look at it