Flex Joint or no?

Nope. “Solid as she goes Capt.”
The only hangers are before the axle and at the end of the tail pipes for 99% of the cars.
A running “drone” is typically wrong gear or camshaft to rear axle ratio (in other words the two are not compatible for the driving you are doing.- my 340 demon did this and I changed the rear axle ratio to a steeper gear and it was gone) or it can be created by other items others here will be glad to tell you.
Syleng1