ON JANUARY 14TH, 2018 I WAS DRIVING FROM TULARE, CA TO MY HOME IN PIXLEY, CA. HALF WAY HOME DRIVING ON HWY 99 I EXPERIENCED THAT MY RPMS WOULD GO DOWN AND MY VEHICLE WOULD SLOW DOWN EVERY SO OFTEN. ON DASH SCREEN I HAD A POP UP THAT READ, 'SERVICE STABILITY CONTROL' DON'T KNOW WHAT THAT MEANS. SOMETIMES NOT BEING ABLE TO SLOW DOWN (FULL CONTROL) I MADE IT TO PIXLEY. STOPPED AT MY SISTERS HOUSE, WHEN LEAVING I WAS BACKING UP AND WHILE BACKING UP I NOTICED A MAIL BOX STAND WITH 2 MAILBOXES ON A STEAL STAND. I DID NOT HAVE CONTROL ON STOPPING THE VEHICLE. I DID SOME DAMAGE ON THE REAR LEFT HAND SIDE OF MY CHEVY TAHOE. I CAREFULLY DROVE THE TAHOE TO MY HOME DOWN THE STREET, PARKED IT AND CALLED CHEVY ROAD SIDE SERVICE. I ALSO NOTICED THAT THE BREAK PEDAL MOVES SIDE TO SIDE AND THE BREAK LIGHTS STAY ON WHEN IN PARK. LUCKILY NOTHING HAPPENED TO MY FAMILY AND I ON OUR WAY HOME. OBVIOUSLY THE VEHICLE IS UNSAFE TO DRIVE.