I have the same problem. I know it's not a manufacturing defect because the phone is capable of vibrating much stronger to indicate an incoming call. I don't know why you can't set the same vibration pattern for a text message, it's very frustrating.

Hi,
i recently bought a Samsung Corby Plus GT-B3410R. when im in class i set the phone on silent so that the phone vibrates when i receive a call/ text. the problem is when i receive a call/text i cant feel the vibrate cuz it's is so weak, even when the phone is pressed up against my leg. is it possible to download longer vibrates :S or make it vibrate harder?

P.s is it possible that its a manufacturing defect