XRAY - Model racing cars

When should I replace my diff outdrives? Mine have a little play with the dog bones and have a feeling I need to replace them. Will this be wasting power if they have "slop" in them?

The outdrives aren't that big of a deal because you're on power about 90% of the time and this means the drive pins will be forced to one area of the outdrives. You will notice a difference if there is so much wear that it keeps the suspension from moving freely while accelerating though. But this will have to be a lot of wear, but you can swap the outdrives left to right sides of the diff, just don't turn the whole diff around!