Core Support

[Bowtie4004x4]

 The core support brackets mounted to the frame on my 78 3/4ton 4x4 are cracked, both of them. The core support itself seems undamaged. I wonder if anyone has an idea of why this happened? Cab mounts/supports were non-existant, I wonder if this caused too much stress on the core brackets? Any thoughts? Thanks!

[Donut]

I would have to say yes, it seems to me quite a bit hangs off the core support.  If your cab mounts and supports were shot and the cab was bouncing, I could see the fenders transmitting some of that stress to the core support.  And whatever trashed the cab mounts were working on the core support also.

[Bowtie4004x4]

And whatever trashed the cab mounts were working on the core support also.

  Rust. Sounds logical, Vibration does more damage than brute force at times. I was thinking more along the lines of alignment/force damage but I'll bet your right. The vibration transmitted from the cab mounts being shot thru the fenders to the support is more than likely the culprit.