All of it. The 10 percent figure you occasionally see is nonsense that a lot of people believe just because they've seen it so much.
Quick Answer. Some things that cause a vehicle's front end to make a clunking noise are worn ball joints, a damaged tie rod, broken or loose sway-bar links, hard or damaged shocks, and faulty shock mounts. An automotive professional can inspect the vehicle's front end to locate the source of the clunk. Continue Reading.
Engine noise under the hood may be caused by loose torque converter bolts, low oil pressure, spark knock or excessive piston clearance. A cracked flywheel on an automatic transmission or excessive connecting rod clearance may also cause an engine to knock. Continue Reading.