Hi
I'm moving the response from your previse question to here. I hope you don't mind.
Answer: I think you have the wrong out drives, looking at your picture you can see that the number 310008 for the out drives you have are those of the older style out drives. The older outdrives had smaller pin holes.
Arrma Differential OLD vs NEW - The Improvements
http://forum.goforit-rc.com/showthread.php?761-Arrma-Differential-OLD-vs-NEW-The-Improvements
Here are the part numbers for building a updated one.
AR310416
ARRMA Differential Gear Idler Gear Set
AR310378
ARRMA Differential Gear Maintenance Set
AR310399 ARRMA Gear Differential Outdrive
AR310020
ARRMA Gasket Diff Case