Building Custom Project Needs Some input from PPL

Building a homeade ATV/gobuggy. Anybody know how a drivetrain in a four-wheel drive ATV works. I need somebody to explain how power gets from the engine to the wheels. I know engine goes to a gearbox using a CVT from there im kinda clueless. Another question is if i can use u-joints instead of a cv-joints shafts bc they are kinda expensive compared to auto u-joints. ANY INPUT FROM ANYBODY IS APPRIECIATED. --Thanks