Your Ball Diff Isn’t Bad… It’s Dirty | Full Rebuild with Sejin

Is your ball diff gritty, notchy, or just not feeling like it used to? In this episode of IAM-RC Tech Talk, Sejin takes a well-used 1/28-scale ball differential completely apart and shows us how he cleans, resurfaces, polishes, greases, rebuilds, and breaks it back in. We start with a diff that feels terrible and find wear grooves in the diff plates where the balls have been riding. Sejin walks through how he removes those grooves, polishes the plates, cleans the components, applies the right amount of ball diff grease, and carefully puts everything back together. Then we seat the rebuilt diff and go through Sejin’s method for establishing a starting adjustment before taking the car back to the track. In this video: 01:05 How a ball differential works 04:30 What worn diff plates look like 08:06 Ball diff teardown and cleaning 13:43 Resurfacing worn diff plates 16:06 Polishing the plates for a smooth surface 21:23 How much ball diff grease to use 22:53 Ball diff reassembly 24:26 Seating and breaking in the rebuilt diff 25:50 Establishing a baseline diff adjustment And yes… there may be a few ball jokes along the way. This is the kind of hands-on maintenance that can bring an old ball diff back to life instead of replacing it. Filmed at IAM-RC Racing & Hobby Shop in Manassas, Virginia. If you race 1/28-scale RC and want to understand not just what to adjust, but why it works, subscribe to IAM-RC Tech Talk for more testing, tuning, setup, and track-side tech. #MiniZ #RC28 #RCRacing #BallDiff #MiniZRacing #IAMRCTechTalk #128Scale