Rattling cat?

Evening all.I have just noticed a rattling/clinking sound coming from under the vehicle (1996 300tdi manual) when driving over broken surfaces(ie 99% off the roads around here).I am pretty sure its nothing mechanical such as the box's or diffs but i seem to remember some one refering to the cat breaking up on the inside and making a similar racket.Is it time to get the defender cat less front pipe or could it be something else un related?

cheers Sean

I had a similar rattle which was more or less constant under normal driving and even sometimes on tickover,not sure on the exhaust setup on yours (mines a 93 RR) but theres an exhaust bracket just next to the rear of the gearbox with a bolt in it.The bolt was loose on mine causing it to vibrate and rattle.Worth a look as i was convinced it was a gearbox problem on mine so was well pleased with the simple repair.