I didn't know what "Frame Beaming" was until I did some research to try to figure out a problem.
When our 2008 Chevy Crew Cab Duramax/Allison truck was new it rode very well for a 3/4 ton truck. But starting at about 30,000 miles the ride began to get gradually worse, especially when not towing. The truck body would sometimes shake excessively as the truck went over a series of small bumps at 45 - 50 MPH. It felt as if one of the tires was not round. The vibration was in the body, not in the steering system. Thinking I may have a tire problem, I put the spare on each wheel position, but it did not make any difference. And when the truck was on smooth new asphalt, there was no shaking. At about 50,000 miles the truck shook so severely one time that it really concerned me. I replaced all the shocks; the severe shaking did not re-occur, but the baseline shaking continued.
I did some on line research, and came across the term "Frame Beaming". This is a harmonic vibration in the body of 1999 to (maybe) current model year Chevy crew cab and extended cab trucks that occurs when the truck encounters a series of regular road bumps at 45 to 50 MPH. Here's a link to a Chevy notice
about this. The solution was new rear body mounts. I did the job myself and it took about 30 minutes. Here's a link to a post in another forum
that gave me the directions I needed:
The new rear body mounts fixed my problem, but I understand that there are other causes of the sort of shaking my truck had (including bad tires, out of balance tires, and weird torque converter operation). However, if your Chevy crew cab or extended cab truck is having odd shaking symptoms, consider "Frame Beaming" as a possible cause.