IT COULD ALSO BE FRONT END ALIGNMENT WHEN YOU LET OFF QUICKLY IT THROWS THE CASTER/ CAMBER OFF ENOUGH TO START A VIOLENT MOVEMENT-YOU MIGHT ALSO CHECK FOR A CRACKED BRACKET WELD ON THE SUSPENSION[ SAME THING IT WON'T SHOW UNTIL THE CAR DROPS BACK DOWN]
UNEVEN AIR PRESSURE ON REAR SLICKS OR FRONT TIRES
I WOULD CHECK EVERY POSSIBILTY BEFORE YOU PUT IT IN THE WALL OR ON IT'S ROOF!!!!!!!!!!!!!!!!!!!!!!!!!!!
SOMETIMES A SIMPLE LITTLE THING CAN KILL YOU VERY QUICKLY
LIVELY