How To: Build an Upgraded RC18T Ball Differential

Posted: May 16, 2015 in How To's
Tags: , , ,

  • July 23 2017 – Image Update: Thank you all the sponsors, subscribers and readers of my blog for your support and patience during the recent missing image debacle caused by Photobucket. I would like to apologise for any inconvenience caused. This article now has all images restored. 

This ‘How To’ article will describe the particular steps and components I use to build an upgraded ball differential for the Team Associated RC18T using aftermarket and stock components. Over the years of owning the RC18T I have built several different combinations of this ball differential with varying results. This particular combination is the best assembly I have built to date in terms of reliability, durability and performance.

This article coincides with the current build article:

Custom Build: RC18T Modified Custom Build – March 2015

I would like to mention that by no means do I claim that my procedures outlined here of building an RC18 ball diff is the best method out there. There may be other enthusiasts who build their ball diffs differently and find great success in their methods. What I can say is that this guide describes my particular method that has been developed and refined to build super smooth, very strong, reliable and high performing ball differentials.

PART 1: COMPONENT SELECTION

Selecting the right components is an important aspect of building or upgrading any RC. For this RC18T ball diff build, the most reliable, durable and best performing components have been sourced and tested through trial and error.

In reference to images below, there is a weight comparison between standard steel bearings by 3Racing (1.1) and the Ceramic Bearings by Boca (1.2). Surprisingly, there is only 0.1 gram difference in weight, however the performance and durability of the ceramic bearings far exceed the steel bearings capabilities. The ceramic ball provides lower friction and increased durability as they have less rolling resistance and can sustain higher operating temperatures than traditional steel bearings.

Boca Ceramic Yellow Seal bearings are used in this build. They are ABEC#1 rated, rubber sealed and have proved to be extremely resilient to harsh operating conditions in other larger scale RC builds. I have used both ‘Avid’ and ‘Acer’ brand ceramic bearings, and have found Boca ceramics to be far superior. They are the most durable, best performing and have the longest service life of any bearing I have previously used.

For a more detailed explanation of the selected components please go to the link below:

Product Review: RC18T Differential & Transmission Components

NOTE: All the parts used in this build are still currently available online as of June 2015.

Parts & Materials Used:

  • x2 (Pairs) eRacing Pro Titanium Differential Outdrives
  • x2 (Sets) Team Associated 18T Diff Rebuild Kits – #ASC21115
  • x2 (Sets) Team Associated 18T Carbide Diff Balls- #ASC21116
  • x2 (Sets) Team Associated 18T Diff & Input Gear – #ASC21022
  • x4 Boca Ceramic Yellow Seal Bearings – #SMR128C-2YS NB2

1.1 – Weight in Grams: 3Racing standard metal shielded bearings

1.2 – Weight in Grams: Boca Ceramic Yellow Seal Bearings

PART 2: DIFFERENTIAL PLATE SURFACE PREP

At first glance the differential plates look shiny and smooth, but on closer inspection you will notice small surface imperfections as result from manufacturing. I prepare these differential plates by dry sanding them on a flat surface first with 800 grit then 1200 grit Silicone Carbide abrasive paper. This is then followed by finish sanding them again with 1200 grit and a small amount of water. This process will remove the surface imperfections and create a super smooth surface and may look close to a polished surface from a distance. I do not polish the diff plates to a high polish, this will create too much slip in the differential once assembled. I leave the very slight sanding marks on the diff plates to help the diff balls ‘grip’ the surface of the diff plates.

Parts & Materials Used:

  • x2 (Sets) Team Associated 18T Diff Rebuild Kits – #ASC21115
  • Silicone Carbide abrasive paper – Wet & Dry (800 &1200 grit)
  • Painters masking tape & wooden blocks
  • Isoprophy alcohol

PART 3: CLEAN ALL COMPONENTS

Make sure that all the components are clean and free from grease and grit.

PART 4: ASSEMBLY OF DIFF PLATES ONTO OUTDRIVES

Parts & Materials Used:

  • x2 (Pairs) eRacing Pro Titanium Differential Outdrives
  • x2 (Sets) Team Associated 18T Diff Rebuild Kits – #ASC21115
  • Tamiya TRF VG Diff Plate Grease – #TAM42170
  • Isoprophy alcohol

PART 5: ASSEMBLY OF DIFF BOLT AND THRUST BEARINGS

To help with the assembly of the tiny components associated with the diff bolt and thrust bearings, I fix the diff bolt onto a block of wood using poster clay. ie; ‘Blu-Tak’

Parts & Materials Used:

  • x2 (Sets) Team Associated 18T Diff Rebuild Kits – #ASC21115
  • Tamiya AW Anti-Wear Grease – #TAM53439
  • Xceed Teflon Grease – #103245

PART 6: FINAL ASSEMBLY OF ALL COMPONENTS

Parts & Materials Used:

  • x2 (Pairs) eRacing Pro Titanium Differential Outdrives (Assembled with diff plates)
  • x2 (Sets) Team Associated 18T Diff Rebuild Kits – #ASC21115
  • x2 (Sets) Team Associated 18T Carbide Diff Balls- #ASC21116
  • x2 (Sets) Team Associated 18T Diff & Input Gear – #ASC21022
  • x4 Boca Ceramic Yellow Seal Bearings – #SMR128C-2YS NB2
  • Loctite 641 Retaining Compound
  • Loctite 222 Threadlocker (Low Strength)
  • Tamiya TRF VG Ball Diff Grease – #TAM42169
  • Tamiya AW Anti-Wear Grease – #TAM53439
  • Isoprophy alcohol

Thank you for checking out this article. I hope it helps readers with some ideas on their next build. If you have questions or need some advice on a particular stage feel free to write a comment below and I will answer them.

Cheers. RC-Christoul

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Comments
  1. Anthony says:

    Epic. Thank you so much.

    Liked by 1 person

  2. Brian Barnes says:

    Your like the Dexter Morgan of differentials. You would have a brain aneurysm watching me put mine together.

    Liked by 1 person

  3. Matt says:

    Hi i love your work.

    Can you tell me what screwdrivers did you use to tighten the diffenrential?

    Like

    • RC-Christo says:

      Hi Matt,

      Thank you for your kind words. The drivers I used for the differential are ‘hex’ drivers. Specifically the size driver I used for the diff bolt was 1.5mm.

      The two main brand drivers I use are made by Arrowmax and Ho Bao.

      Hope this helps. Let me know if you need further info.

      Cheers.C

      Like

  4. Paul H says:

    Hi Christo, loving your work 🙂
    One question, the diff rebuild kits, do you find the hole in the centre of the bearing washers is too big? to me it looks like a potential pinch point between the bolt and the inner hole shoulder. I’d have expected the I/D of the washers to be much closer the O/D of the bolt.
    Thoughts?
    Paul

    Like

    • RC-Christo says:

      Hey Paul,

      Thanks for reading my blog and your kind feedback 🙂

      Interesting question Paul, When I get back home later today I will share my thoughts with you.

      Cheers,
      C

      Like

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