Possible problem?

Also posted on TSN but here seems busier atm so apologies if you have read it over there

Last night coming home I thought the car sounded a little more 'whine-y' than usual so asked my mechanic to have a listen this morning as I didn't want to keep driving it and do serious damage.

The sound is coming from the back of the engine low down and whilst linked to engine speeed is a lower frequency 'drum drum drum' with about 2 noises a second at tickover. He's going to shove it on his ramp and see if he can geta better idea of where its coming from.

Anyone experienced anything similar?

Now the gearbox has a years warranty which runs out next month......

I obviously hope its just me being paranoid and theres nothing wrong but I doubt I'm that lucky. In which case here's hoping its the box and the garage don't fight the warranty claim.