Here is a link in German .. scroll down when you see an axle picture with an "I" , [ for information] .. click on it and you will see the reason for the self center roller on the right axle I spoke of ;
It is painly seen with their pictoral geometric picture. Note the red C/L as the swing goes through the arc. They have English tanslator ....

http://213.239.220.84/bin/dbframes.phtml?mid=IN02

I think someone put a right axle in the left side at one time ...

What is the problem with the diff . to begin with??

?