I just bought a 2006 endeavor with 18,800 miles on it and it is the best ride I have had in a long time. One problem is when I slow down sometimes I get a low vibration in the engine and it gives a deep buzz in the radio speakers. I tried adjusting the bass and the treble, but I don't think that is it. Does anyone know what it could be? It does not last long only when it seems the engine is downshifting. Thanks all and Happy New Year to you.