I HAVE A 1999 CHEVY TAHOE. THE STEERING WHEEL JERKS ITSELF LIKE SOMEONE GRABS THE STEERING WHEEL. IT IS VERY NOTICEABLE ON TWO LANE CURVY ROADS. IT FEELS LIKE THE TRUCK HITS A PATCH OF ICE. I HAVE NOT HAD IT REPAIRED YET BUT WAS TOLD BY A SERVICE ADVISER THAT MY TRUCK HAS SPEED SENSITIVE STEERING - IT HAS AN ELECTRICAL WIRE HOOKED TO THE POWER STEERING PUMP TO PROVIDE SLOW DRIVING ASSISTANCE. I AM TOLD THAT IT SOUNDS LIKE THE SENSOR OR EVO SENSOR FOR THIS SYSTEM IS BAD. I HAVE REPLACED THE POWER STEERING PUMP TO NO AVAIL. MY STEP DAUGHTER HAS A 1997 CHEVY 1/2 TON PICK UP WITH THE SAME PROBLEM. SHE HAS HAD DOBBS AUTO DISCONNECT THE SYSTEM. I THINK THIS IS VERY DANGEROUS ESPECIALLY IF YOU OVER- CORRECT WHEN THE PRESSURE CHANGES OR BRIEFLY GIVES WAY AS I WOULD DESCRIBE. I WONDER HOW MANY CRASHES ARE CAUSED DO TO THIS GREMLIN IN THE STEERING SYSTEM. THE SERVICE MANAGER AS MY LOCAL CHEVY DEALER SEEMS TO BE AWARE OF THIS PROBLEM. *NM