the cause of this is probably a bad u joint
check CV joints
A hole in the muffler would cause a knocking sound in your muffler. A loose exhaust pipe can also cause a knocking noise.
A seized gear can cause a knocking sound on a 1987 Nissan 5 speed transmission. A blown gasket can also cause this sound.
It's a little vague, but check your u-joints, that would cause a sound when driving.
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can you elaborate? engine noise? stationary/moving? ticking, tapping or a definite knocking?
change fuel pump
Most likely you need a new strut
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.
low oil and a loose piston skirt
My 2000 Grand Prix would have a low-speed knocking noise coming from the drivers side as the CV axle was failing. The loss of lubrication in the CV Boots allows the joint to make a knocking/tapping sound at a low speed. If the knocking is coming from the engine compartment, then it could be an entirely different problem.
Most common cause would be a loose brake caliper mounting bolts.