Chevy express Towing U-haul flatbed w/ 4650LB trailblazer

That can is a 7200 gvw 2500 van. In a nut shell, a light duty van. Does not have same frame suspension as a 2500 pickup, or 3500 van. That can has same suspension frame etc as a 1500 pickup.
Depending upon what you are pulling, yes, 6000-7000 is probably all that van is rated for.
It also probably has 3.98 axle gears, vs the two optional of 3.42 or 3.73.

It's probably with running from.

My 02

Marty