Grand Caravan Highway Vibration

I have a well maintained 1999 Grand Caravan with 135,000 that has served me well. The problem frustrating my mechanic and I is this: During my last road trip of about 1200 miles in all, the van sometimes starts to vibrate at about 55 - 65 mph, slowly at first, then gradually more intense. It fells like the vibration is coming from the rear. I pull to the side of the road wait a minute or two and get back on the road with out any further vibration. During the 1200 mile trip this may have happened about 3 or 4 times. Each time with the same sequence of events. Of course the vibration happens hundreds of miles away from my mechanic. He drove the van midway through my trip and said it drives well with all systems seemingly in order especially the front end components, struts etc. This intermittent vibration is most puzzling, please help this father be at peace while driving with his family.

Thank you.

I had this same problem on our 99 Plymouth Grand Voyager. I went crazy trying to figure out what it was. It would vibrate violently, then I’d pull over to stop, and start again and it would run fine. Then at some random time later, it would happen again.

It turned out to be old-weakened brake spring hardware in the rear drum brakes. Something I read (a tsb or technical discussion) led me to look at the brake hardware. I bought new brake spring hardware, along with new shoes, and never had the problem again.

Thank you Joe for the quick response. I will take your info about the brake spring hardware to my mechanic and look forward to the smooth vibration free driving.