NOTE: There has been a mold adjustment to the diff case which may eliminate the need for the below process.
We only use our Class 12.9 screws when building diffs, which also resolved this issue by allowing the ring gear and case to be clamped together tighter. We consider them a necessity for durability, so either way, your diff will work perfectly out of the package if you are using the Class 12.9 screws we carry.
The HD diffs now include a gasket, but the molded plastic case that contains the sun and spider gears remains unchanged. The added space within the assembly due to the gasket thickness doesn't allow for the gears to properly mesh.
This results in an excessively notchy feel that can even lead to stuck or skipped gears as things shift around inside the housing.
Grab a differential and turn the outdrives back and forth while tugging outward on them. For an even better evaluation, hold the ring gear and pull/turn the opposite outdrive.
If it feels notchy or becomes stuck while pulling outward and turning, but smooth when pushing the outdrives inward and turning, your gears aren't meshed close enough.
Wet sand your differential housing so that the width ends up between 12.6 - 12.7 mm. That's the sweet spot we've found across numerous diffs we've worked on, but it could vary. We like to err on the lower end of that range.
Once things are at the point where operation feels smooth even while you tug outward on the outdrives, you're good to go. Reinstall and race!
