Rattle from Suspension/Brakes?

A very common rattle for Subarus is from the heat shields suspended beneath the catalytic converter. This rattle can seem like it's coming from anywhere beneath the car. While there are lots of possibilities, this is one to check out. You don't have many miles on the odometer, but your car has been on the roads taking a licking for for at least five years.

ok you said it happens only on rough surfaces.

first i will agree with John T. sway bars on these do rattle. they will seem alright but they rattle. so check that out.

second check your front struts. they sometimes have a play in the strut shafts which causes a clunk. lift your wheels up and rock it hard top to bottom ( one hand at the bottom of tyre and the other hand on the top ) without taking the wheels off. check the shaft top nut also. we repair a lot of these and 90% of this clunk is caused by shaft play. the rear ones does this as well.

probably the brake pads rattling. they have little stops that keep them from falling out that can sometimes become loose, letting them rattle. autozone sells some adhesive to spray on the back of the pads to stop the rattle, but you have to take the caliper apart.

you might also want to check your sway bars. these tend to give off more of a "clunk" noise when going over bumps, but could cause a rattle too. i know my freinds 'rex clunks and rattles cuase of the sawy bar, and i think its a commom problem for these cars