HD Differentials: Almost Perfect

Learn about a potential issue with the LC Racing HD differentials, and how to adjust them for flawless function.

With the release of the L6260 HD differential set in 2022 (included in all current RTRs and kits), the ring/pinion wear has been drastically improved, in part by eliminating the flex in the ring gear by using a one-piece design.

However...

A new issue arose. The HD diffs now include a gasket, but the molded plastic housing 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, as well as some awful sounds (and wear).

The Test

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 glitchy or becomes stuck while pulling outward and turning, but smooth when pushing the outdrives inward and turning, your gears aren't meshed close enough.

The Solution

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!