growling noise when braking

I have a 2003. Mine does the same thing. Sounds like its coming from trnamission area. Only with the rear brake as well. I try not to use the rear brakes cause it does,nt sound good. I'm thinking maybe the bearing on the rear of the output shaft but thats just a guess. I did notice that I get good engine braking if I crank up the idle. When engine braking is working the problem disappears. The only problem with that is the idle has to be cranked up after I have it in gear or it will grind going into gear. Just ride along and slowly turn idle adjustment up gradually going down a small hill until engine braking kicks in. Then I just turn it back down when I have to disengage the trans. The book says 1400 +/- 100 rpm but I have to get it higher than that for the engine braking to work.