rumbling from underneath

Does anyone else get an intermittent rumbling from under the van while it is idling? The sound seems to be coming from the rear of the van and it sounds like what you would hear when the antilock kicks in but not as loud. It is hard to trace and with the window open it does not sound like it is coming from the engine compartment but I can't imaging it coming from anywhere else. The vehicle is stopped completely. It happens whether the vehicle is in gear or not. Any help on this would be appreciated.

What you may be hearing is the automatic leveling system. The compressor pump is located in the left rear corner of the vehicle behind the tire. It will activate at random to maintain a proper level. It only runs for a few seconds at a time. Is you vehicle equipped with compresser option? Hope this helps.......

Thanks for the help but unfortunately I do not have the load leveler package on this vehicle. I will continue to see if I can hunt it down though.

Check the exhaust system, you may have a broken hanger causing it to vibrate. This will sound like a rumble in the rear of the vehicle. Also if your spare is mounted underneath the van it could have come loose and is vibrating as well.