I have an L3O with an IRS rear axle. I treied to change spur gears, but the diff rings did not ride on the balls. I tried 3 different spur gears, and had the same result. I'm not sure what I am doing wrong. I have the correct diff balls, and Nothing seemed to help. Any Ideas?

Are you sure you have the right sice diff balls. They should be 1/8 " or .125 with calipers. Also if you have the d ring make sure the rings are lined up with the hubs. What kind of spur gear are you using.

I don't have the D ring axle, just regular round one, and the gears are made by rwspeed or something like that. I have the 1/8" balls, but the rings do not ride on them. I'm not sure if the gear is cut too thick or something.

Are the gears thicker than the balls or are the gears made for somthing else. Do the rings tighten up to the gear or are they loose when you tighten the diff nut. If there loose than maybe you have a flanged bearing in the spur gear which makes it to thick and won't let you tighten the diff all the way down.

the rings tighten up on the gear.

Gears must be for another type of car,sounds like there too thick. Make sure there for a pan car