We have a relatively small 2WD 24 foot Class C and take it on dirt/gravel/rough roads whenever we have to rockhounding. We also just plain like to explore and camp "out there".
We do it only in dry weather, and do so by driving very slowly and carefully - especially on heavily washboarded surfaces. Going fast "to smooth out the washboard jolting" doesn't work with a heavy vehicle that's full of stuff. Even given that driving style, we have done mods to our cabinet doors to insure that they stay closed and have a lot of rubber shelf cushioning material stuffed in between loose items in the cabinets. I believe that in our case Winnebago mounts it's cabinets directly onto the metal struts within the coach walls ... because we've never noticed any loosening of coach cabinets, furniture, or appliances.
I also use non-stock tires with a larger diameter in order to raise the entire rig just a bit for improved ground clearance. We especially looked for and purchased a small Class C on the Ford E450 chassis (see my comments below).
Here's some of my thoughts on a Class C to be taken off-highway:
1. 4WD is the "ultimate" addition to a Class C .... however, 4WD conversions raise the overall center of gravity of the Class C ... which is not the best for travel on tipped/canted road surfaces or when weaving through deep road ruts. Also, on any road, a higher Class C is more unstable in high cross winds and when big trucks pass. I wish they could install a 4X4 conversion on a Class C without having to lift it so much.
2. Assuming the 4X4 conversion was done with the minimum lift necessary only to make physical room for the additional drive components ... then use larger diameter tires to increase ground clearance for all the RV's critical under-coach and chassis components. Doing these two things together will get to the best compromise configuration of - a low as possible center of gravity 4WD Class C with greater than stock ground clearance everywhere for critical coach and chassis components.
3. Start with a small as you can tolerate Class C, but on the more rugged Ford E450 chassis instead of the usual E350 chassis. This chassis gives you a wider rear dually stance for added lateral stability on tipped road surfaces ... plus this wider stance may also allow for the rear duallies to more often ride on the top of the ruts instead of down in them. The E450 chassis has more swept area for it's brakes and has a larger diameter drive shaft. It also has a lower ratio rear differential to help counter-act larger diameter tires so as to maintain slow speed pulling power and provide less transmission slippage (which can result in higher transmission temperatures).
4. But here's the main reason for opting for the E450 chassis under a small Class C used off-highway: It's frame uses thicker steel to provide a stiffer flat platform under the coach. This can help to minimize or eliminate any twisting of the coach structure when traveling on rutted roads - especially if you take it real slow and pick your path very carefully ... as you should.
As the OP probably knows, there is no substitute for traveling out in the middle of nowhere and then being able to stay right there with all the comforts of home in any weather!
2005 E450 Itasca 24V Class C
