SAE rating is not written in stone. SAE is just a set of standards for measuring-- those measurements will still have a tolerance. You're jeep is built to SAE standard inch pattern tolerances and guess what not every Jeep is exactly the same. So, your point shows me you've never worked with any manufacturing process otherwise you would know just as I do that advertised power or torque is often less than or greater than what you get out of an engine. Because of various factors found within the manufacturing process.

I don't think what you're doing is garbage. I just think you need to realize that when you take into account all the possible areas for margin of error in the process you will find that 33% drivetrain loss is pretty high. Usually, most studies show less loss than that in a drive train.