Originally posted by MarNaDaKi
Aluma :
Trust me, you don't want to deal with the diff outdrives
http://www2.towerhobbies.com/cgi-bin...=++&search3=Go
of the gear diff. They are as soft as butter. Even the suppose-to-be-option hardened ones are softer. The problem is that the slot become wider and wider to the point where the dogbone interfere the diff action by wanting to get stock inside it. Don't know how to explain it better. 
Now, what's wrong with plastic outdrives ? I wanted to get rid of my steel outdrives in favor of plastic ones and you want to replace your plastic one for steel ones. 
I really don't think that was the issue that Aluma was concerning about. What he meant as the plastic outdrives were actually Tamiya barestock dogbones with plastic ends on it (I don't remember having those in the rally car, Aluma). The way you were describing me about outdrives being worn out, I can take that you never use the rubber O ring that supposed to be there to prevent the dog bones in the first place. Thus, Tamiya does not offer plastic outdrives other than for EVO3, 414 series and the TA04 series.
About the super smooth diff action..I think that's just the ball bearings, man!