If your back end is coming loose you could have a suspension problem. I never had that problem until recently I notice the ride getting worse, cornering not so great and I did have the back end come loose around a corner that should have been a piece of cake. Turns out I had a broken rear coil spring. 2 new one in the rear and the car drives good as new. Back end is glued to the road.
1995 E420 - retired
1986 420SEL - retired