Here are a couple of short videos of me setting up the mysterious side thrust on the differential that applies to all styles of the Classic Mini Cooper transmission. Once you understand the goal of having no side PLAY in the diff without any side LOAD on the bearings, correct set up just depends on attention to detail and having a reasonable assortment of shims, about two gearboxes worth….
This first video is the conventional way to set them up, pretty much the way the manuals tell you to do it:
This next clip is a different way of looking at doing the math, with the idea being to reduce the amount of “stuff” to assemble to simplify and reduce the chance of making a mistake. Or, simply another way of looking at arriving at the correct shim may help you understand what’s important, and you’ll find a way to do it that makes sense to you!