What are the causes of the rattling noise in a transmission vehicle?
2 Answers
The causes of the rattling noise in a transmission vehicle are: 1. Excessive clearance between the piston and cylinder wall; 2. Over-tight assembly of the piston pin or connecting rod bearing; 3. Wear of the cam profile in the valve train; 4. Cracked camshaft timing gear or loose fixing nut; 5. Loose connecting rod bearing, melted bearing shell, or incorrect size causing rotation; 6. Piston knocking against the cylinder wall or loose connecting rod bearing; 7. Piston ring leakage or broken piston pin; 8. Severely loose flywheel fixing bolts; 9. Loose crankshaft bearing or melted bearing shell; 10. Loose crankshaft bearing; 11. Severely loose connecting rod bearing cap fixing bolts or completely melted and detached connecting rod bearing shell alloy.
As a veteran driver with decades of experience driving manual transmissions, I've encountered many cases of transmissions making rattling noises. The most common causes are loose chains or worn gears, especially in older cars that have traveled over a hundred thousand kilometers. The sound is like a continuous tapping, particularly noticeable when going uphill or accelerating. Worn chains develop gaps, creating noise during rotation. If not tightened or replaced promptly, they can accelerate damage to other components. Another issue is insufficient lubrication—aged or leaking gear oil increases friction, leading to abnormal noises. I recommend regularly checking chain tension and fluid levels, and trying to tighten the chain bolts yourself if possible. Additionally, if you frequently drive under high loads, internal bearings or synchronizers in the transmission might be failing, so it's best to get it repaired early to avoid major issues. Using high-quality lubricants during repairs can extend the lifespan.
