new noise? can any one help

iv just been out in my 90, and when i take my foot off the accelerator then the engine rev decrees i start to get a sort of grinding noise, iv just got home and jacked it up and it looks like one brake pad is very low. Would this be the noise or is it something more expensive?

Thanks

Henry

Does it happen above a certain speed? Check your UJ's

just when slowing down not at a certain speed, and the ujs look ok to me.

I would say a transmission whine, you're just not hearing it over the engine when it revs!
Try disconnecting props and checking for play/grinding in diff's and boxes