XRAY - Model racing cars

Just got back into racing after 3 years away from the hobbie, Basically when i used to build diffs i always sanded down the rings but i cant remember what sandpaper i used to use, Any ideas? im pretty sure it was around 1200 just so the rings wasnt completelly smooth so no need to tighten the diff as much before slipping.

there is too much playing with ball diff
buy geardiff
it will be better and easier

I seem to recall 600grit

i personally use 1600 but 1200 is probably about right.

What about different types of grease, I.e thin vs thicker?

The Associated black stuff is good, or their Stealth grease.

The method that I have perfected is as follows;-

1. With the ring on the output shaft use a dremel with the disc cutting tool on its face to remove the grove.

2. Clean off ring still attached to the output shaft.

3. Replace cutting tool on dremel with a circular buffing tool. Apply some cutting compound on the face of the buffing tool and polish the diff ring.

4. Clean of any excess polish.

5. Repeat for 1-4 for other diff ring.

This give super smooth ring like new. Rebuild diff with new balls and you'll have yourself a super smooth diff as good as new.

I'll post some pictures to detail further detail my method and to show the results.
Ps The cutting compound is used for removing overspray / polishing car bodywork and can be purchased from most automative car stores.

That sounds like a good idea, As for the polishing i was once told that if you sand the rings so taht they are smooth but still have a slight scratch to them this will help grip the balls which will then mean you wont have to tighten the diff so much. Is this idea totally wrong?

I've successfully used this method on 3 diff rebuilds. So far I have not experienced any problems with the balls or diff slipping.

But again I would stress that it is important to change the 12 diff balls to guarantee as super smooth diff action!


Michael