At idle, when in motion, I hear a slight rattle from under the vehicle?

There is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.

MY CONCERN WOULD BE THE DIFF LEAK!

THIS AIN'T YOU WINDSHIELD WASHER RESERVOIR LEAKING LEAKING

AS FAR AS THE RATTLE,

GO UNDER ABS START SHAKING STUFF

EVEN GO AS FAR AS USING SAFETY WIRE/ ETC WIRE, MAYBE LOOPING IT TO THE FRAME AND OVER SUSPECT COMPONENTS---WITH A SCREWDRIVER, HOOK IT IN THE MIDDLE OF YOUR LOOP AND "TWIST IT" TIGHT (AS YOU DO TO TENSION THE CORNER POSTS OF A BARBED WIRE FENCE) JUST ENOUGH TO "TENSION" A POSSIBLE SHAKING TAIL PIPE, ETC. WE DON'T WANNA BEND STUFF! ONCE YOU ELIMINATE THE SOUND, FIGURE OUT A PERMANENT SOLUTION W/ HANGERS AND SUCH........IT VERY WELL MAY BE THE INNARDS OF YOUR CATS

KEEP US POSTED ON PROGRESS

FIX YOUR LEAK.....OR IT MAY JUST SIT THERE RUNNING AND NOT RATTLE, UNABLE TO MOVE

I'LL SHOW YOU WHAT "LACK OF OIL" DID TO MY TRANSFER CASE IN THE LINK BELOW, THIS WAS CAUSED BY ME DISTURBING "TOO MUCH" RVT GASKET USED BY THE PREVIOUS OWNER TO INSTALL HIS TRANSFER CASE COVERS (NOW "MY").

I SIMPLY SNATCHED THE TRANSFER CASE AND TRANNY....SO I COULD REBUILD THE TRANNY. WHEN BOTH UNITS WERE RE-INSTALLED, THE MUMMIFIED RVT HAD COME LOOSE IN THE BOTTOM OF THE "UNTOUCHED" TRANSFER CASE.

WHEN FILLED BOTH BACK UP W/ 85/90. THE LOOSE RVT STOPPED UP THE OIL PORTS ON THE TAIL-SHAFT PORTION. I HAD NO SYMPTOMS ON MY 10 MILE DRIVE.

THEN SUDDENLY THERE WERE A FEW SQUEALS, SOME CRUNCHIN' SOUNDS......THEN THE DRIVE-SHAFT SUDDENLY STOPPED AT 55 MPH. MY "CAT-LIKE" REFLEXES KEPT MY JEEP UNDER CONTROL AS IT WANTED TO SLIDE SIDEWAYS INTO THE OTHER LANE........THIS ALL TOOK PLACE IN A MATTER OF SECONDS!

THIS WAS EXPENSIVE FOR ME, THE TREMENDOUS TORQUE UPON LOCK UP, BUSTED THE MAIN CAST IRON CASE TOO. I DID ALL OF MY OWN REPAIRS, IT WAS STILL EXPENSIVE!

SEE PICS "JAN 9 2012" AT THIS POST

https://www.2carpros.com/questions/1992-ford-crown-victoria-aod-transmission-time-shift-2nd-gear-roughly-30mph-locks

THE MEDIC