V8S transmisson noise

[seb400]

My transmission has started making occasional noisy clunking sounds. It's most noticeable when pulling away from stationary with a resounding loud clunk. I'm sure that the UJs are okay as the car doesn't 'shunt' in normal driving, or when coming on/off the accelerator. Has anyone had significant drive-shaft/exhaust contact? I'm wondering if tired engine mounts might be a possible contributor?

Steve