The mileage on my Preve Turbo is about 31,000km now and the sound from the gearbox, more like low-frequency humming is getting louder. Also the acceleration is not as smooth. Although it is not exactly serious or worrying, it is an observation which shows that the gearbox may be changing in character. I don't know if I should wait until the next scheduled service about 5 more months to get the guys at the service centre to look at the problem.

A caveat is I frequently do hard acceleration with the car. But that should not contribute to the slightly unsmooth and louder operation of the gearbox of the car unless the quality of the CVT is not very good. I did not encounter any problem with my previous Nissan Sylphy of 5 years which I also frequently do hard acceleration. THe gearbox is smooth as silk and silent (I still recall the nice-sounding sound from the engine when the car was accelerating hard in Sports mode).

Did you encounter the gearbox changing character at around 30,000km to 60,00km when compared the car in new condition ie. less than 20,000km mileage?

My new Preve Exec have noise (sounds like metal twisting and 'clarking') when going through bumpy road. The noise is from the back. Is that normal?

Can you describe what are the symptoms of "gear slipping". Do you often drive your car hard?

FWIW almost 3 years of ownership with the car I believe this Preve Turbo's CVT is not very suitable to be driven hard. Occasionally yes, but not frequently. Not too sure about others but in my experience the CVT will show some anomalies and act weird if it is subject to frequent hard acceleration. Some signs are the CVT showing louder sound even when you drive slow, weird whining/louder sound and a slightly jerky drive.

I still drive the car with frequent burst of acceleration everyday, but not as hard as before. I'm worried about the reliability of the CVT which doesn't seem too robust from the way it is acting now.

Check with SC bro. Proton claims their CVT tech is from belgium ( same cvt provider to land rover, volvo, volkswagen ect) not from proton itself.  Ask sc to check your engine. Otherwise, go to the respective car wash and clean your engine.. I did once and the problem solved.