I have a 89 K5 Blazer with new brake pads up front, new rear shoes in back, and a new brake master cylinder. The problem I'm having is when I use the brakes on slippery roads, all 4 tires are locking up at the same time. My brake calipers and wheel cylinders are fine and my axle seals aren't leaking. I've never experienced this kind of braking condition before. I was told by a guy I know that he thinks it's my vacuum brake booster? I figured if it was the booster, that I would have an extremely hard brake pedal? Please help ASAP as there is snow here and it's kind of uncomfortable to brake on snow and ice. Thanks, Doug 4 wheelin's not a job, it's an adventure!