Hey everyone,

I have a 1999 5-speed 2 door 4x4 Blazer. Truck has 245k miles on it, engine has only about 175k.

This morning on my way to school I noticed when I decelerate, from about 35 mph down to 10 mph (1.5 RPM to 0.5 RPM) my truck vibrates a good amount. Dash, steering wheel, and door panels shake. it almost feels like the vibration when you take off into first gear and don't give it enough gas.

This vibration happens when I'm on OR off the brakes, therefore I'm convinced it's not the brakes. It also happens when simply coasting to a stop. When I accelerate at any point during the slowing down process the vibration instantly goes away. The truck does not vibrate when you're on the gas. Also, does not matter if I'm in neutral, or downshifting through the gears.

I'm thinking it's an idle problem... any thoughts?

 

I'd look at the u-joints...

 

I checked it out on a lift today. I turned both front wheels and the back ones turned too. It was stuck in 4 wheel drive, but my in dash switch said 2 Hi. Found out the vacuum switch was holding pressure and keeping the front diff. engaged. Pulled out the line and it released. It was a bad switch, and I just replaced it from GM a month ago. Thanks anyways guys.