Quote Originally Posted by lakay
Timing belt is used in mostly high reving engine because of smoothness in transmitting rotation from crankshaft pulley to accessory drives like camshaft. Its a lot more quieter than the timing chain or timing gear, and that is also the main reason why luxury cars like lexus, infiniti, acura or cadillac uses them. The trade off is that you have to have it replace when it reach a certain mileage (km) or hours of operation.

Timing chain is used in medium reving engine like Sentra, or other small block engine. They are a little bit noiseier than than the belt, but they last a lot longer, specially if proper lubrication is maintained.

Timing gear is used mostly on diesel engine due to high torque that is being generated by the engine, plus it can take a lot of punishment before breaking. Most big block engine like Tractor trailer (18 wheeler) or electric generators which can run forever as long as it properly lubricated.

Not many car manufacturer is using timing chain anymore due to fact that customer like you and me, like the quietness of our driving. It only hit us on the back side of our cranial when it due for replacement. It cost an arm and a leg to get replace.
well said