Strengthening the EMB & LC12B1 Drivetrain

Updated: Oct 15, 2025

Make your differentials and gearboxes as bulletproof as possible with these upgrades.

What's Needed

While the LC Racing lineup is incredibly durable as a whole compared to every other small scale brand (including Arrma's Grom collection), there are a couple areas we wanted to make even stronger.

Gearboxes

Whether you hit a wall at high speed, or don't quite land that big air backflip onto concrete, if the shock towers take serious impacts, the gearbox will eventually break, and most likely in the manner shown.

It's a fairly quick fix, but we prefer to upgrade.

Differential Case Screws

Something we didn't realize was an issue until it started occurring on practically every one of our rental vehicles: the little M1.4 screws (of unknown metallurgy) that secure the ring gear to the diff case can easily break.

Because the screws shear off and leave half of themselves stuck in the case, you'll need a new diff case, and since they're HD diffs, you need to sand them down first to accommodate the gasket width before re-assembling.

This likely occurs due to hard driving where an abrupt stop/start or change in RPM occurs, such as landing a jump while on the brakes/throttle on a high traction surface, or just crashing into things at high speed.

The heavy metal ring gear needs to be clamped to the plastic diff case well enough that there's no side load applied to the screws. It's a steep request for the tiny stock hardware.

Installing M1.6 Diff Case Screws

The existing diff case holes don't need to be drilled any larger, but they do need an M1.6-0.35 tap ran through them to prepare for installation.
The new screws use an oddball 1.3 mm hex key rather than the original Phillips screws, but this makes for a much smoother installation with greatly reduced chance of stripping.

Installing Heavy Duty Aluminum Gearboxes

Remove the upper deck and set aside by removing the 4 screws at the front and rear using a 2 mm hex driver.
The two longer screws that go into the steering posts may prove more challenging, as the posts will likely spin if they don't quickly break free.
If that happens, you'll need to use a 1.5 mm hex driver on the bottom screws that go into the steering posts. Things just get more in the way if the posts end up coming along for the ride, but it's OK.
Rear upper deck screws.
Move the upper deck out of the way to gain better access to the gearbox screws.
Remove the spur cover.
Remove the bearing support insert.
Remove the 4 screws holding the rear gearbox to the chassis.
The whole rear assembly is now removable from the rest of the vehicle.
Remove the 6 screws holding the upper gearbox to the lower.
Remove the 4 screws holding the shock tower to the upper gearbox.
Now's a good time to upgrade those dogbones to CVAs, if you haven't already. You'll see how annoying it is to line up both ends of the dogbone when reinstalling everything. :)
Remove the front and rear suspension mounting plates.
Install the plates onto the new gearbox. Use a small amount of removable threadlocker on every screw that goes into them throughout the assembly.

In the unlikely event that you need to shim the ring and pinion gear closer, this is where you would place the 10 x 12 mm shim(s).
Arms and plates reinstalled.
Reinstall the 4 screws holding the tower to the upper gearbox.
Have fun getting the dogbones back into the outdrives of the diff and the axles at the hubs.
Reinstall the 6 screws holding the upper gearbox to the lower. Screw heads may slightly rub the upper housing relief cuts during installation, creating a pulsating feel when tightening with a powered screwdriver. It's okay; power through it. We wanted to make these gearboxes fully compatible with the OEM plastic gearboxes, so all hole positions are identical. However, the material thickness around the screws cannot be made any thinner without compromising integrity or creating an opening, so the little rub is a necessary evil.
Set the gearbox back in place on the chassis, ensuring the alignment pins are in the holes of the chassis, and the center driveshaft is back in its cup (not that important if you're also doing the front, as it's gonna fall out again before this install is over). Tighten the mounting screws through the chassis.
The front can be a little more annoying because you have to work around the steering. Multiple ways to do it. Here we just remove the ball studs on the steering links.
Same process, same 4 screws need to be removed.
And the front is off. Make sure not to lose the bearings on the steering post. Easy to forget and reinstall everything without them, and things will be wonky.
Otherwise, it's the same process as the rear.
Be sure to place the center driveshaft back in both front and rear cups.
Critical Note
The rear suspension plate of the front assembly is a little snug with the chassis (at the red arrows). Ensure alignment pins are as close to flush as possible with chassis before installing screws to avoid cross-threading or seizing.