There’s no updates to the TSB; it’s basic vacuum system diagnosis. If you’re going through multiple check valves I’d suspect you have a leak in the system that is drawing debris and moisture through the check valve and causing it to fail.I've had this TSB done a year ago. I'm on my 3rd vacuum check valve and now the symptom (2WD front end grinding/rubbing noise) is back. I ordered 2 more check valves and I know the grinding will disappear for about a year then it will come back.
@FordTechOne -- do you know if there is an update to this TSB at all? Any recommendations to try to get this fixed once and for all?