Drivetrain, gears and axles for HYPER GO RC cars

Where the load goes, and where it stops

Torque leaves the motor at the pinion, crosses to the spur gear, splits at the differential and reaches the wheels through the drive shafts. Four handovers, four wear points. On a brushless 4WD truck that lands from a kerb, the shafts take the shock and the spur takes the heat.

Nothing on this shelf is a performance upgrade. These are the parts that return a vehicle to how it left us.

Spur gears and pinions come as a pair for a reason

Our spur gears are powder metallurgy rather than moulded plastic, and each ships with its steel pinion. Fitting a fresh spur against a worn pinion gives you a mismatched mesh, a whine you can hear across a car park, and a second failure inside a few packs.

Set the mesh with a strip of paper between the teeth, tighten, pull the paper out. That is the whole method and it has not changed in forty years.

Sealed differentials

The 16420Y is a complete, sealed differential for the 1/14 and 1/16 family. You fit the unit rather than a bag of loose gears, which keeps the grease where it belongs and removes the one rebuild most owners get wrong.

A differential that clicks under power has lost a tooth or its grease. Replace it; cleaning and repacking a unit that has already skipped buys you one more run.

CVD shafts and portal axles

Drive shafts are supplied as metal CVD sets — the 16410 pair for the H16PL and H16BM, the 16410S four piece set when you want both ends done at once. Constant velocity joints hold their speed through steering angle instead of surging, which is what keeps a 4WD car tracking straight under power.

For the H12Y crawler family the equivalent part is a complete right front portal axle assembly, supplied built. Portals raise the axle line above the hub centre, which is where a crawler's ground clearance comes from.

Symptoms worth reading before you order

A grinding noise that follows throttle rather than road speed is gear mesh. A click that follows road speed is a differential or a shaft. A vibration that appears only above half throttle is usually a bent shaft, not an unbalanced wheel.

If the car pulls to one side under acceleration and runs straight off throttle, one front shaft is binding. That one is worth catching early, because a binding joint will take the hub carrier with it.

Checking fitment before you buy

Every card on this page lists the chassis it suits, and the filter on the left will cut the shelf down to your model code. Drivetrain parts are the least forgiving items we sell — a shaft two millimetres long will fit and then destroy a diff cup.

Where a card shows no price, the item is between runs. Write to the address in our footer and we will tell you where it is rather than leaving you to guess.

Chassis codes this shelf serves

The 16410 and 16410S CVD sets are cut for the H16PL and the H16BM. The 16420Y differential covers the 1/14 and 1/16 families, which includes the H14BM. The portal axle assembly is a crawler part and goes nowhere near the brushless trucks.

All of these sit behind a brushless motor delivering its torque in spikes rather than in a smooth line. That is why the materials here are metal and powder metallurgy rather than moulded plastic, and why a 4WD car punishes its drivetrain more than a two wheel drive one ever did.

Narrowing this shelf

The filter on the left lists chassis codes and whether an item is priced today. Drivetrain stock moves in batches, so a card without a price is usually a limited gap between runs.

Size is the thing photographs hide. A shaft two millimetres long will go in and then destroy a differential cup, so trust the code on your chassis plate over anything you can see on screen.

When a noise is not what it looks like

Send us a short video with the body off and the wheels turning. Sound carries the data a photograph cannot, and we can usually name the part from it.

Our contact details are in the footer and the customer who writes before ordering spends less than the one who orders twice. Please include the model code; everything on this site is keyed to it.

What the drivetrain is working against

On an MJX HYPER GO car the maximum load on these parts arrives in the first half second of throttle and again on every landing. The battery delivers it, the speed control meters it, and the suspension decides how much of it reaches the gears as a spike rather than as a push.

That is why a 4WD RTR truck eats shafts where a slower car never would, and why the protective sealing on the electronics has nothing to say about it. Keep the tires fresh, keep the arms straight, and the drivetrain lasts much longer off-road than the numbers suggest.

Our side of the transaction

Our services are stock, answers and replacements, in that order. If an item is between runs the card says so rather than quietly accepting an order we cannot fill, and we will tell you when the next batch lands if you ask.

If a part arrived damaged, our first action is a replacement rather than an inspection. Nobody has yet needed to post a broken gear back to us to secure one, and the screw kits on the hardware shelf cover the fasteners that go with the job.