I want to build a 4x4 truck

You want to build a 4x4 truck with suspension, a working transmission with 2WD (preferably RWD) and 4WD selectable, and high and low range capabilities, but you're unsure which LEGO set to start with. You're looking for a non-motorized version and find the Land Rover transmission to be too complex for your project.

The challenge lies in finding a LEGO set that provides the mechanical components you need without the added complexity of a motorized system. You're aiming to use a pre-existing set as a base and then modify it to create your custom 4x4 truck. The ideal set would include the necessary suspension and transmission features, allowing you to focus on the truck's design and bodywork.

Since the Land Rover transmission is too complex, you'll need to explore other sets that offer simpler, yet functional, transmission systems. Consider researching Technic sets, as they often include the gears and mechanisms needed for 4x4 functionality. Look for sets that feature selectable drive modes (2WD/4WD) and potentially a high/low range, which are key features for your truck build.

To get started, you might want to look at sets that feature independent suspension systems. This will give your truck the off-road capabilities you're looking for. Once you find a set with the right mechanical components, you can then focus on designing the truck's body and customizing it to your liking. You might also find some helpful guides or tutorials online to assist with your build. You'll definitely need a brick separator to take apart and rebuild your sets.