I get a pretty hard clunk only when it downshifts to 1st when throttling out of a slow turn or corner. If I ease into the gas, the downshift has no clunk. I've looked at all the drivetrain mounts and universals and everything is tight.
Nice van! I have basically the same conversion van. The roof rack might have its challenges as there aren't many options for gutter mounts. The fiberglass top might support the weight if distributed properly. Wheel options are probably a little better with the 17x9.