Can anyone give me an idea what this problem might be, may be a needle in a haystack but any help would be great.

Car is a 2000 UK Classic with about 45k on the clock.
My mates car.
Problem - He was driving along under a medium load when he heard an almighty crack from the rear of the car , and from then on a loud whining noise from the same area. He got the car home ,but is no longer driving it as not to cause anymore damage.
He has had a quick look underneath but cannot see any fluids leaking from anywhere.

Any ideas?

Cheers

Paul.