Tamiya F104X1 Build – Part 2 – Differential

The Build – Part 2
In step 2 we will be building the differential. This is the most important feature of your F104X1. A poorly built diff will result in a horrible handling car. Take your time here.

Build Notes:
Grease is your friend when building the differential. Don’t be afraid to put a little extra on the balls and rings. Any excess will spin its way off.

Prep the two wheel mounts by screwing the set screw in place. A little dab of blue loctite should be applied to both set screws.

Slide the axle into place. Notice the orientation of the flat spots on the axle. It should be inserted as shown.

Slide the right side wheel adapter onto the axle. Align the setscrew with the flat spot on the axle and tighten down.

Insert a bearing on each end of the counterweight.

Slide the counterweight into place as shown. Don’t forget to add the small spacer inbetween the counterweight and the axle height spacer.

Slide the left side wheel adapter into place, align the setscrew with the flat spot on the axle and tighten. There is a small tolerance to where the setscrew tightens down on the flatspot. Use this to adjust the wheel adapters to allow about a 1mm side-to-side movement of the axle.

Attach the right side diff hub. Align the setscrew hole with the notch in the hub.

Drop the diff ring into place and key it to the hub. Apply a little silicone diff grease to the diff ring.

Slide the other diff ring onto the outer diff hub and key it into place. Then slide the bearing into the hub.

Apply diff grease into all the holes in the spur gear. Take one diff ball and place it into place on the spur gear.

Insert a bearing into the spur gear and slide onto the axle. Take the outer diff hub and slide it on the axle behind the gear. Insert another bearing followed by the 2 cone washers and diff spacer. Notice the direction of the 2 cone washers. They need to be ‘facing’ each other. Finish the assembly with the locknut. Fully tighten the locknut and then back off a quarter turn. Hold both hubs (it’s easier if you slide the wheels on the hubs first) and try to turn the spur gear. It should not move at all. This is a good starting setup.

Insert the setscrew into the diff cap. Make sure you add a dab of blue loctite.

Insert the diff cap, lining up the setscrew with the ‘middle hole’ on the outer diff housing. The middle hole is defined as the one on the ‘corner’ part of the outer diff hub. Once in place, slide the axle pin through the other hole and center. Lock the pin into place with the setscrew.

Part 3 – Installing the motor.
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