I've recently noticed a "thunking" sound when I let out the clutch from a start or into/out of 1st and 2nd gear in my 05 MCSc. When speeds go up, the noise seems to disappear when I engage the clutch.

Any ideas?

 

It could possibly be the engine and tranny mounts. I would check those first. When they go bad, especially in 1st and 2nd, engaging the clutch while shifting will cause the tranny or engine to jerk. Try going full throttle in 1st up to around 5k rpm, then let go of the throttle fast. If the engine "bounces" more than 1 time, they may be worn out. When my upper engine mount broke. Those were my exact symptoms. It was the easiest thing I've ever had to fix.