Grandfather and grandson levitated in dump truck.

This happened somewhat early in my childhood. My Grandfather was doing the groundwork for the Pleasant Hill Dairy Queen.  Earlier that morning my Grandmother had mentioned she had to go to the bank that is also located in Pleasant Hill. He had finished his CAT work and unhitched the trailer from the dump truck and we proceeded to move out east on hwy 58 to go home. We had gotten to the intersection of hwy 58 and Tillicum, as that street is called now, and I felt something weird in my tummy, like on a roller coaster ride. I remember saying "what happened?" My Grandpa then said, "look down there, there's your grandma." There was no seat belt laws back then so I stood up in the cab of the truck and crawled over to my grandpa's lap and looked down. I could see the top of the bank and could see my grandma's Buick going into the drive-thru at the bank. I could also see east down the hwy, we were at what I believe to be now at 200-250 ft up above the hwy. I remember seeing the top of a tractor trailer rig and the tops of a few cars. I also remember looking down on the telephone poles. This lasted maybe 10-15 seconds and then we were back on the hwy traveling at speed moving eastbound. I immediately asked my grandpa "How did we do that, what did I touch?" He responded with, "What's that?" You see it was pretty loud in those old dump trucks. I said, "How'd we go way up in the air!!?" I stood up and started trying to mess with some buttons. He then said,"Quit messing with that stuff , get up on your seat and just hold still!" It seems he had no recollection of the event. We got home a few minutes ahead of my grandma and when she arrived I excitedly told her what happened. She said,"(grandpa's name), whats he talking about?" Grandpa responded "I don't know he's been going on about being up in the air or something rather since we got back." I told her grandpa didn't believe me and I was pretty upset. When my parent's came to get me I immediately told them what had happened but I still wasn't believe! d. I can remember that day vividly. Sadly my grandpa passed away in 1998. I used to ask him about that day when stuff like that came up. He never recalled that experience. I don't know what happened that day but it was the first of several unexplained event's in my life. Just thought I would share.
Witness indicates that the date of the sighting is approximate.  PD