Don't know if its been mentioned, I haven't read all posts. I ALWAYS use the clutch when engaging/disengaging overdrive. I do this as I once owned a Sunbeam Rapier which had a bad oil leak. .End story gearbox main shaft badly twisted on the splines which I reckon was caused by the previous owner not using the clutch( I know because he took me for a drive before I bought it ) and the shock loading was too much.