A Centre Differential for the Wltoys 104001: Parts and Assembly

After the 104001 review, the next step was to revisit a modification I had used in my other car: adding a centre differential. This documents the assembly; the electronics conversion comes later.

Parts for This Installation

I used an original 104001 differential, an LC Racing spur gear and two dogbones: 100mm at the rear and 70mm at the front in the final assembly. I also reused drive cups and a bearing from the original centre transmission.

The new spur has different teeth from the original. The motor pinion must match it: touching teeth do not establish correct meshing. The links below are references from the description; check variants and dimensions before ordering.

Preparing the Differential

I opened the differential and transferred the cup to the new spur, retaining the seal, washer and pin. After replacing the internal gear, I started all screws before tightening progressively in a cross pattern.

I checked rotation and added the bearing recovered from the original transmission. Keep the small parts accounted for throughout.

Changing the Transmission Connections

I removed the top plate and spur covers, then replaced the original centre connections with the cups for the new dogbones. Some parts were very difficult to remove; I dismantled part of the steering to gain access.

When fitting the cups, I checked the shaft flats and screw seating. Before continuing I verified that turning each cup moved the wheels without abnormal resistance.

The Top Plate Needs Clearance

The original plate rubbed against the new assembly. I relieved the interfering areas and tested movement before closing. The video offers no universal cutting dimensions: trial-fit the actual combination and check clearance.

I fitted the long dogbone at the rear and the short one at the front, then checked motor position and gear mesh.

The Spur Remains Exposed

The original covers no longer fit this arrangement, leaving the spur exposed to stones and dirt that could damage its teeth. The modification has trade-offs.

Keep wiring clear too: neither motor wires nor the battery balance lead can approach the transmission. My car still had the original electronics at this stage.

What Is Checked Here

I bench-checked differential operation and movement distribution between the axles. I did not drive this configuration with the original motor and pinion. I already intended to replace them; the meshing heard during the presentation was not ready for driving.

Next is the 104001 brushless conversion, where I complete the electronics installation and service all three differentials.

Video Parts and Spares

The cups and gear are spare references in case of damage during dismantling, rather than an instruction to buy the entire assembly again.