All the BLX6s diffs are the same*. Follow the Senton video above, it will get you there. I think Thomas even has part # for the shims he uses. *there are two different ratios for the diffs. The 3 big wheel trucks use 13t/43t gears, the small wheel cars use 10t/43t. The bearings, diff cups, and all the internals are the same, though.