There are a few specialty manufacturers but prices are a little crazy.
As mentioned previously a couple things negate the benefits of manufacturers producing 4x4 versions:
The house an many won't stand up to any serious off road work. Once the frame starts flexing you quickly run into problems with it holding together. Google: Unimog RV and you will see what it takes to make a true off road RV. Probably overkill for what you need but you will find most keep the house separate and use a 3 point support system so the frame can flex independent of the house.
If it's just a bit of extra traction you are looking for, it's probably not needed or easily achieved thru other means:
- A typical pickup might carry 40% of it's weight on the rear axle. Since traction is coefficient of friction times weight, you have traction equal to roughly 40% of the rear tire with the least available traction. By engaging 4x4, you get 100% of the tire with the least available traction or about 150% more traction.
- On a Class C, it's probably closer to 70% on the rear axle, so you already start with around 75% more traction. If you think you need more, get a limited slip diff or better a locking diff, you address those situations where one wheel is in mud or loose sand and can often double the available traction.
Ultimiately a 4x4 will do better but if you are thinking of an empty pickup as a comparison, the class c will already have far more traction as a percentage of overall weight.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV