The fourth rule,,, Undoubtably and understandably, you’ve encountered this imposter 4th rule. It’s hard to ignore but worth the effort. Since this fourth rule is so established, you’re probably not even aware of it. How it came to be I am unsure. Nothing better for you and your drive line to ignore it completely. There’s a whole bunch of basic ground rules before getting to these 3 rules. Your situation will differ slightly from the next guy and those are basically established ride height and operating weight, setting up on relatively level surfaces and having some decent equipment and measurements. It’s all basic stuff but different ways to achieve it. Those aren’t what I’m getting into. Each rule is based on the one prior beginning with level at ride height then rule #1. No rules violate each other, ever. That’s why they are rules. You can find the 3 rules on any driveline site, be careful to spot rule 4 even there. I’ll do my best to help you spot this 4th rule but I can’t help you ignore it though it’s best that you should. The first rule is “everything viewed from the transmission to the rear”. ((( the term everything means everything ))) The second rule is - down slope (rule 1) are negative and up slope ( rule 1) are positive. ((( up and Down hasn’t been changed))) The third rule is math “ when the slopes are both (rule 1&2) negative - subtract the smaller from the larger, when both slopes are both (rule 1&2) positive you subtract the larger from the smaller , if slopes are opposing meaning one (rule 1&2) positive and one (rule 1&2) negative then you must add. ((( negative and positive always have same meaning,, clearly defined in rule 1&2))) There’s 3 simple rules, only 3 and each based on the one prior. Don’t play with anything like an unspoken 4th rule and you’ll be fine. Don’t switch meanings or exclude anything from the term “everything” and you’ll be fine. Don’t deviate from rule 1 in any way. Perfect every single time, pretty simple and easy. Especially don’t add a fourth rule that violates any parameter set forth in rule 1, 2, 3. Spotting the 4th rule out in the wild. That sabotaging imposter 4th rule would include a violation of rule 1 and thus changing directions. The imposter sabotaging 4th rule would require that you violate rule 2 and call that negative slope on the pinion as up. The imposter sabotaging 4th rule would require you to violate rule 3 exactly correctly (((( can one violate any rule exactly correctly))) or fuck everything up, get confused, seek help and run into nothing but confusion with other confused people explaining why or which parts of sabotaging imposter rule 4 is more important. Stay away from rule 4, ignore the many pictures you’ll undoubtedly find of rule 4, you’ll be fine if you know rule 4 when you see it. Rule 4 is not rule #1, but sometimes you’ll see folks using rule 4 as their own guide. That’s as simple and to the point as I can get it. Go ahead and play with rule 4 if you must, if you learned rule 4 before learning 1,2,3 then you’ll most likely have to explain why rule 4 is relevant and how to navigate rule 4 to achieve a correct outcome.