Something is rattling inside my Sisan French steamer,it still works. Do I need to figure out what is rattling and get it out?

it could be an exhaust heat shield rattling or some part of the exhaust. you will have to look and hit things to find the rattle. is there something inside the rear of the car that can cause the rattle.

Might be Exhaust, but if Exhaust is loose , you usualy here a rattle when you are also driving the car on the road. Best to take Car to local Repairer , put Car on ramp , and take a look , as it could be something else that Rattles.

What is a center (sic) locker? Does it rattle when this something is off? Does "front" mean from the engine area- audible inside the vehicle?
Trying to help

finding noises is hard work and is ART.
get help.
1;: is it the dash it self, press on it, doe that stop of change pitch of sound.
no?
2: i must be something inside. use a cheap rubber hose to your ear.
and move hose all over dash underneath to find the true source.
you never said under what conditions, it rattles.
parked (rats/mice....), idling,, moving, or only bumps in road.
or only during earth quakes, (LOL)

Rattle noise is hiting something? Yes you can buy on line a flex pipe or a mufflet shop will fix it. But if it rattles inside it could be your catalyst

Sorry for the late reply but, no, it is not related to a loose heat shield. It is a louder rattling sound more like a loose bearing vibrating inside either the transmission or the clutch assembly. Only between 1600 and 1900 rpm. and it is not present under ou over these rpm. The rattle desappear when I lock the 4X4. Dealer is out of solution!!

sometimes the muffler will have a broken weld inside and let the guts rattle around,normally if you rap it with something it will rattle inside if its the problem

Usually this type concern is a exhaust heat shield loose or damaged or components inside the exhaust system damaged or a faulty motor/transaxle mount.

the rattleing was the pump dying probably. find the leak whether a hose or the pump. replace and see if it works fine.

Replace the clockspring in the column.