I recently started to hear some chattering noises. At first I thought it was a valve, then my mechanic put a few sound probes here and there and he tells me he thinks it's coming from between the transmission and engine. He tells me the engine runs too smoothe for valves and he listend very carefully to the head with this probe he used. The chattering is worse in 1st and 2nd gear or right when I turn on the car. In the rest of the gears you can bearely hear, or hear it at all, until you get on it above 5000rpm. Any suggestions?