Assembly Instructions - Page 6, Step 1
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Step 1 shows how to assemble the rear differential on the rear axle. The rear axle assembly will be completed in Step 2.
Step 1
The first step involves building the rear differential. Find the #73403 parts tree, it's the one with the small bevel gears and pinion gears on it. Using a hobby knife with a fresh blade or a pair of side-cutters (these are basically very sharp wire cutters that are used only for plastic parts), carefully cut off the small bevel gears that go inside the spur gear/diff housing. Be careful to cut away the thinnest part of the tree, not the small nub that holds the gear in place inside the diff housing.
Use the tip of the knife to apply grease from the grease tube to the bevel gears or the diff housing where the bevel gears will sit. It doesn't matter which one you put the grease on, as long as you have a nice coating of grease to lubricate the gears.
After you're done installing the bevel gears in place, apply a little more grease to the gear teeth and set the spur gear aside.
Find the axle in your hardware box and the left side of the gear diff (the wide bevel gear with the hex on one side) and slide the gear over the axle as shown in the instructions.
Next, slide the spur gear over the right side of the axle.
Then you can slide the right side of the gear diff over the axle, enclosing the gear diff.
If you are using the Viper GTS-R body or just want a wider stance in the rear for your car, use the 1mm spacers from the wheel hub tree (the black parts tree with 4 large circular parts on it). The 1mm spacers are in between the wheel hubs.
Install the plastic spacer in one of the rear wheel hubs (one of the wider wheel hubs, not the narrow wheel hub!). It's easier if you install the spacer before you put the hub on the axle. Use your thumb or the wrench on the #73404 parts tree to press the spacer in place. The spacer needs to be fully seated before you install the wheel hub.
Put the right rear wheel hub on, then screw the nut onto the rear axle with your fingers. Hold the middle of the axle with a pair of pliers and use the Micro wrench to firmly attach the nut.
When it is on pretty tight and the wheel has no wobble on it, unscrew the bolt one full turn and check the wheel hub. There should be a very small amount of wobble on the axle. If the diff nut is too tight, your car will not handle as it should, so take your time on this step!
