In the interest of practicing some PM and listening to the sounds my
van makes I pose this question.

I am hearing a new sound in my 87 Westy.  At freeway speeds (65
MPH'ish) going downhill if I lift completely off the accelerator I
hear a sort of low pitched rumble from the back of the van.  It's not
terribly loud and I do not feel any vibration.  It doesn't exhibit
this anytime other than freeway speeds.

Where should I be looking?  CV joint possibly?

Thanks in advance,
-Roger Donahe