[David Hodgson]

Chris, I don't know how much noise there "should" be but you are right, it is exacerbated by the solid mounting of the diff housing and even more magnified when I fitted the single hoop roll bar which has the inner mount socket welded right next to the diff top mount. When I finish the rollbar I will fill it with expanding foam to try and deaden the ring.
I guess thats why vehicle manufacturers refer to suspension bushes and engine mounts as "insulators".