When I press the brakes in my 97 4Runner, my front end shakes, sometimes violently. I thought it was warped rotors, but the shaking doesn't happen all the time. A local mechanic told me if it didn't happen all the time, then it wasn't the rotors. He looked underneath and said he saw where a bolt had worn and gave some play in the axle. I don't recall the name of this bolt, but it is part of a bolt & strap system that performs some kind of stabilizing function for the front axle. The whole car shakes when it brakes, but it's definitely coming from the front end, and my steering wheel shakes pretty bad, but no real vibration in the brakes. Anyone ever heard of something like this? Any idea on the cost to fix it? The local mechanic thought somewhere in the neighborhood of $1200 if it was indeed that bolt because a whole new part would need to be ordered.

I had the same problem on my 2000 and finally fixed it simply by swapping in a different brand of brake pads.

There was a TSB for 3rd gen front end brake vibration. Apparently some brake pads leave uneven deposits on the discs resulting in vibration when braking.

If your vibration comes and goes, then your rotors are probably fine and all you need to do is get some new brake pads.