The combination of fuel still being pumped into the engine and air
You forgot to let your wife in
It's really hard to understand what you're asking here."What causes a knocking sound when your car drops into a hole while driving?"If that's your question, I imagine that it would be the sound of your car dropping into a hole.
Gearbox oil needs changing.
Bad CV joint, loose rim, Loose caliper
If it only happens when backing up, you may have the parking brake engaged.
The 2 most likely: A. Timing is off. B. Oil is low.
Check the drive axle for a broken and leaking boot or bad CV joint.
You need to get your car checked.
Bad ball joint
Because it just does. That's why.
your car being broke get it checked out
Get it fixed.