I have a 2005 Ford Expedition that is making a loud noise from the front passenger side. It's not exactly a grinding, but best description I can come up with is a washboard type sound. It only lasts a few seconds and is very intermittent, usually at higher speeds and sometimes when making a slight turn or curve to the right. After reading this, we replaced the solenoid which did not take care of the problem. The vacuum appears to be fine. We have it in the shop and they have replaced the wheel bearing and the axle shaft. The noise is still happening, again very randomly. This is our family vehicle and I do not feel safe driving it. Any suggestions?