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The 410R was originally rumoured to come supplied with more typical ball-type differentials which you'll pretty much see on every other 2 & 4WD racing chassis these days.  Whilst I was pretty interested to test the differences I'm also just as happy to find the 410R is instead supplied with the same sealed oil-filled gear differentials as it's big brother. 

These gear-differentials have proven super robust in the previous car although not as entirely fit-and-forget as first thought since they will need re-filling occasionally - thankfully that's not a major job and it's not like a ball differential which all needs cleaning and setting/re-setting after a rebuild.

The differentials go together well - using plenty of the supplied grease on the input shafts and oil-seals. The main gears slide with slight difficulty onto the hexagonal-shaped input shafts - they actually go on easier than first impressions suggest since the more you try to force them on the harder it is. Getting the gears on properly so the input shaft is flush with the top of the gear is important to avoid excess play and help seal the diffs up properly.

Of course the beauty of the gear-differentials are the ability to fill them with different viscosity oils to tune their performance - commonly with a heavier oil up front and lighter in the rear. The kit-supplied oil is pretty thin and I wanted something a little thicker (a mistake probably given the first race I was going to take it to would be on a loose dirt surface). I went with 10K in the rear and 15K up front and marked the differentials cases so I knew which was which for when it came time to drop them into their respective gear cases.

The centre driveshafts on the 410R are the first real change from the 410 and are actually an upgrade on the original kits items.  All the CVD's on the 'R' feature heavy duty 2mm pins with vastly improved 'flats' to ensure they won't back out during use.  To 100% guarantee this, the centre shafts are also supplied with plastic sleeves which simply slide over the joint after assembly to prevent the pins from backing out even if the grub screw were to fail.
We had a problem with the rear shaft on the original car when a pin came loose and ground it's way deep into one of the lipo saddle packs - which sadly ended it's life.  That shouldn't be a problem any longer with these new sleeves.  The CVD's assemble much like any others and exactly the same as the originals - the only thing to remember is to place the plastic sleeve over the gearbox-end of the driveshaft before assembly - something I forgot a grand total of 4 times! (on 2 drive shafts, a record?).

The plastic sleeves are a tight fit and the sharp leading edge makes them hard to fit the first time - I just ran a sharp knife around the inner edge to make them easier to install.

The plastic sleeves I found to be a nightmare to fit unless you modify them slightly I found - a really light scrape around the inner lip to give a slight bevel to help slide it over the shaft is alll that's needed but it's definitely best to assemble the sleeve over the unassembled shaft once to loosen things up and make it easier once it's all together.

The assembled driveshafts are mated up with the gearbox input shaft which again is steel just like on the DEX410 and means the whole drivetrain (apart from the spur gear obviously) is steel and won't fail in any conditions we can conceive.

The diffs and input shafts drop into the 2-part plastic gearbox cases for later in the build.

Diff unit and centre shaft assemble into the 2-part gearbox.

The only difference between gearboxes is the length of the centre shaft - and oil used to set diff action.

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