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Here is showing you how to use Micro Finishing Film to Grind & Polish the 1/12 Diff. Ring.

This is the Associated Diff Ring ( 12LW). The ring is “cone”when punched out during in the manufacturing process. So, we need to use the micro finishing film to “grind” it flat.
Besides, we need to gently "rough" the surface, so the steel / ceramic balls can grab on the rings instead of slipping.

We use Micro Finishing film because it provide a better Bearing Surface area on the diff rings than conventional abrasive sand paper. But, it is a bit costly.

You diff now run super smooth, and you don't need to over-tighten your nut, the balls also last longer.

thanks for posting this. I knew that diff rings needed some work to make them flat, but I didn't realize just how bad the stock part is.

Nice write-up.

I do this to all of my diffs and they stay smooth for a very long time. I use 400 grit sand paper to get it flat, then go to 800 grit to finish it off. My Vonats RC10 was done like this, and afetr about 4 hours of runtime, it still feels like butta...

Simichrome metal polish works great for finer work, and Wenol works pretty well for more coarse of work.

Thanks for the tip. This should help salvage hard to hard to find dif rings for our antiques....including my mr4bc-s.

There is a guy in Ohio doing this for most of the late model cars b4,b44,rb5 etc www.bfastrc.com

covell2 wrote:There is a guy in Ohio doing this for most of the late model cars b4,b44,rb5 etc http://www.bfastrc.com

Why spend extra bucks for something that can be done with your own hands ?

camlchris wrote:

covell2 wrote:There is a guy in Ohio doing this for most of the late model cars b4,b44,rb5 etc http://www.bfastrc.com

Why spend extra bucks for something that can be done with your own hands ?

same reason so many people buy rtr's and not kits these days. i'm right there with ya chris i would much rather do as much as i can myself and have the extra money to spend on parts i need.

To each his own but for about 20 bucks you get carbide diff balls in the package, and if you think that the current associated and kyosho diff balls are of good quality your mistaken. I have run the bfast stuff in my b4 all last year and have not touched the diff not once.

covell2 wrote:To each his own but for about 20 bucks you get carbide diff balls in the package, and if you think that the current associated and kyosho diff balls are of good quality your mistaken. I have run the bfast stuff in my b4 all last year and have not touched the diff not once.

US$20.00 for the ring + carbide balls ? I think, I can offer u the rings + ceramic balls at this price.

really I have never run ceramic diff balls are they good? I would like to try them.

covell2 wrote:really I have never run ceramic diff balls are they good? I would like to try them.

I used the carbide balls before ( from AE) on my 1/12 CRC Gen.X , but they don't last long. ( I think, they last for appox. 20 to 30 times of 8 minutes run).
Then I switch to cermaic balls , now over 30 times of 8 min. run, still in perfect condition ! Super smooth ! More importanly, it cost less than the AE carbide balls. i got from the LHS the cermaic balls is just around US$ 8.00 for 8 or 10 balls ( i forget how many balls in the package. )

In the buggy application, I am not sure if this work out great like the 1/12 on road. As the buggy suffer a lot a force from jumps on the ramp.

They might not last as long who knows. When I used to run pan cars back in the late 80's they used to make ceramic diff rings and they where extremely expensive. Pretty sure the associated carbide diff balls are chinese in origin and are no where near the quality they used to be.

I've been running the same 12 ceramic diff balls in my B4 for 2 years now, they last a little while I haven't gotten around to doing the diff ring sanding, thrust ring sanding, ceramic everything yet but that was a good start and a noticeable difference.

Brandon G wrote:Nice write-up.

I do this to all of my diffs and they stay smooth for a very long time. I use 400 grit sand paper to get it flat, then go to 800 grit to finish it off. My Vonats RC10 was done like this, and afetr about 4 hours of runtime, it still feels like butta...

Yup, brandon did my diff too, I freshened it up with new lube after I got home from the VONATS and it's back to buttery smooth goodness! I've never ran as many battery packs through a car at one race as I did at the VONATS, I wish I would have brought more tires!! (Thanks Hoopty for helping me out with some!!!)