DIY: Bullet proof diff//Raider XL

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Arrma RC's
  1. Raider
Parts needed:

If you already have the Raider XL then the parts needed are actually minimal...keep that in mind within this list...

Diff-case Arrma #AR310003 (x1 set)

Gear-Set Arrma #AR310009 (Need x2 sets)
Includes: o-rings, shims,pins as well as a set of bevel & spyder gears.

Ofna crosspins #355080 (x1 set)

10x15x4mm bearings HPI #b030 (x2 each)

Outdrive Arrma #AR310008 (x1 set)
You'll need to drill out the hole in the outdrive to accept the fatter pin from the Arrma gear-set, allowing for the bevel gear to be installed.
I suggest heat treating these while they are out before assembly. This requires a small vise and a torch. If you are unsure of this or too young i highly recommend NOT attempting this. Not doing the heat treatment wont hurt anything. This is only to prolong the longevity of the outdrives.


The 6x80mm Arrma dogbones from the Raider XL seem to be too short & small in diameter. Just enough to trash both the outdrive and stub axles.
The HPI dogbones i used which are 8x86mm fit but are a little to long making for +positive camber which cannot be adjusted.

I have a set of 8x32 on order and will post my findings when those arrive.

Ive been testing my diff out which is filled with Castrol HypoyC automotive gear oil with great success.


Insert the O-rings into the case internally on both sides. No O-ring is used on the outdrives for this mod. Put a drop of oil onto the outdrive shaft and o-rings.

Slide the outdrive into the diffcase halves.

Put the shims onto the outdrives.

With needle nose pliers put the pin through the outdrive.

Pop the bigger bevel gear over the outdrive and pin. It will lock into its place!

**Spyder-gear assembly**

This is where the Ofna crosspins come into play!

Slide the smaller spyder gears onto the crosspin making sure to follow it with the small shim.
Put this into the differential unit with the notched slot facing up towards you.

Repeat the steps to make another spyder gear set. Place this over the other set already in the diffcase, only this time with the Ofna crosspin slot facing down. These will all align into place with minimal pressure on top holding it in place.

Fill the lower diffcase with your favorite differential fluid.

With the gasket on the diff-case, carefully assemble the 2 halves together and using the x4 screws to finish it up.

Thought i'd throw this in this DIY article for those unfamiliar with the process.


In the illustration i uploaded it shows small internal shims. Ignore that as the 2014spec gear set comes with much bigger O.D. shims.

This is also the 2-spyder setup.

Using the Ofna crosspins allow for a total of x4 spyder gears and x2 bevel gears.

The O-rings also shown before the bearing & on the external diff casings will not be used either. Only the internal O-rings can and will be used.


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New problem arises! Lol

The bulletproof diff is awesome but now... My stub axles are litterly falling apart chunk by chunk. Grinded it down a few times to hopefully stop it from further damage but also the sharp edges after it busts up?

Arrma drivetrain parts suck. Period.
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