Saturday, February 6, 2016

Product Showcase: Usukani Rear Shaft Conversion Kit for Sakura D4

There is no doubt that the 3 Racing Sakura D4 has taken off since it was introduced. The same can be said for Usukani. This young brand has gained interest and momentum worldwide in a short amount of time. They have put a lot of focus on the Sakura D4 and are delivering unique upgrades for this popular chassis. Usukani's latest and most significant upgrade to date is the Rear Shaft Conversion Kit for the Sakura D4. They are producing it in Pink, Black, Silver, Yokomo Blue, and Red. The USA pricing on this little gem is a mere $78.

This kit is very comprehensive, and replaces the entire rear drive section and bulkhead on the D4.

It comes packaged neatly, and protects the finish on all the parts nicely.

And there are a lot of parts!

The kit includes:
-Instructions for both the shaft conversion and using the stock belt drive
-All spacers required
-Center gear unit
-Rear axle + gear
-Spur gear mount + shaft
-Metal bevel gears
-Multi-hole rear link mounts
-Bearings + shims
-Metal outdrive cups
-Rear axle bearing mounts
-Rear pulley style eccentric bearing mounts
-All screws, pins, and hardware needed to build the unit

It is hard to believe that all these parts can be included in a kit that costs $78 USD. Let's build it!

The heart of the conversion kit is the center bevel gear unit. It assembles in a straightforward manner and goes together pretty easily. TIP: The bearings fit pretty snug in this assembly, so make sure to clean any dirt that may have found it's way into the bearing seats. Carefully press them in and make sure they are seated all the way.

Personally I would have liked to have seen this assembly use some shims for adjustment so that I could fine tune the mesh at each end to suit my preferences, but the Usukani assembly gives an acceptable mesh at both ends without the use of shims. The large bevel gear that goes up top is metal that comes with a black coating on it, and the lower gear is a plastic Yokomo 17T gear.

The rear axle and gear assembly is a pretty standard affair. It features an aluminum center and metal outer drive cups. It also uses a standard Yokomo 40T plastic gear that should be easy to source for replacement when the time comes. The Usukani Rear Shaft Conversion Kit does change the gearing of the drivetrain. The stock D4 uses a 32/16 pulley ratio that works out to a 2.06 reduction, while the Usukani kit uses a 40/17 gear ratio that works out to a 2.35 reduction. In my case I was using a 92T spur and 22T pinion making the FDR 8.61. With the Usukani shaft conversion the FDR changes to 9.83, so I am planning on going up a couple of teeth on the motor pinion gear to compensate.

The kit includes some M2 x 4mm screws to hold the bevel gear on to the axle that require a 1.3mm hex tool. I did not have a quality 1.3mm hex tool on hand, and felt like I was going to round out the hexes on the screws while tightening them. Luckily I had some alternate screws lying around with deeper hexes that used a 1.5mm tool.

The rest of the assembly is straightforward and goes together without any issues. The only tricky part is making sure that the bearings are all seated well and completely. The fits are snug, so careful attention needs to be paid there. Also, be mindful when installing the M1.6 screws that hold the axle bearing retainers in place. The threads can strip easily if over-tightened. I chose to keep the original D4 round spacers because I preferred the look of them over the kit supplied parts. They are interchangeable, so that gives you more options on how to assemble the kit. I also substituted stainless screws throughout. The kit supplied screws are good quality, and the only reason I switched them out was to match the rest of my chassis.

Here is one area where I think this kit provides a real value: extra parts and instructions are included to install the factory D4 belt drive components. So if you prefer the belt drive, or have a breakage and are waiting on replacement parts, you can just swap in the belt drive setup and be back in action again. I built it up with the belt configuration to demonstrate how easy it is and how well it goes together.

Once assembled the Usukani Rear Shaft Drive Conversion Kit fits perfectly into the D4 chassis. I used the innermost mounting holes for the upper turnbuckles and my original alignment was retained perfectly.

One thing you will notice immediately, besides how good it all looks, is that the rear of the chassis is now extremely rigid compared to the factory plastic parts used for the bulkheads. I am anxious to get to the track and test it is out, and will provide feedback once I do. It is still hard to believe that you can get all these parts that fit together so well for only $78. Any other manufacturer would charge 2-3X more for what you get in this kit.


  1. That looks super sweet man. I can't wait to get mine in.

  2. Cool looking part, but what does to change in driving terms? Thanks

    1. The biggest benefits will be from the extra rigidity in the chassis and having some optional upper turnbuckle mounting spots. Some prefer a gear drive over the belt and vice-versa, so that part amounts to personal preference.

  3. Please visit the Usukani Facebook page for a listing of retailers worldwide.

  4. these seem to be out of stock everywhere :( Nice write up. :)

  5. I have a lot in stock
    Facebook :Shilun Gu

  6. Hi RexRacer Great Blog
    Our local Hobby store has just built a Drift track so was looking at getting into it for some bad weather and evening fun/laughs Never drifted but have been racing at local road track. Have read a fair bit about the D4 and have read your blog, Just a quick question in regards to your upgrades Those Usukani bits look great. Would it be possible to do a list of what would be needed immediately (seems like knuckles and lower arms would be) Thinking I might keep my first drifter fairly basic and if I get into it I might just build a complete new car from scratch no kit as it seems your car wont have to many original parts left. But from what ive seen this is the best D4 build out there.

    1. Galvo,
      Thanks! Glad you like the blog. To be honest the D4 slides nice right out of the box. If you followed my build, you will see a video with me sliding it completely stock, and with a good setup it can work well. For the most basic mods, I would look at aluminum steering wipers, and maybe some Usukani or Eagle Racing lower arms to get a little more lock. If you want to spend more, get some Usukani knuckles up front and call it done. Decide if you like drifting and keep it basic before going nuts with mods. Hope this helps.

  7. how many tooth you use for the spur and pinion?

  8. The Yokomo gear diff D150 fits in pretty easy. The outdrives are a little shorter. If paired with D3 arms it fits nice.