Originally Posted by DOTMAN

This was from the Tamiya site:


TRF 415 Ball Diff
Tamiya America is fully aware that many of our U.S. customers are racing on carpet. As we have found it is preffered to have a ball diff in the front for best performance. At this time Tamiya does not offer a front diff as both the Asian and European markets have no need. This is due to the fact that racers in those markets run mostly on sweeping high speed flowing tracks, hence the dominant choice of one-way cars.

Interim solution
In the interim, Tamiya America recommends the following Yokomo parts to directly fit a ball diff on your 415.
YOK-ZS-501 complete diff half's
YOK-ZC-507 diff thrust bearing set
YOK-ZS-508 diff adjusting kit
The stock Tamiya 415 diff rings will work with these parts as well as the stock rear pulley. Note: depending on what suspension arm system you use it may be necessary to use either 42mm or 46mm universal swing shafts. This is a interim solution and we hope you find it useful. For you TCS racers out there, please note that this modification is not TCS legal