Hpi Rs4 Mt Ball Diff Options

[rbmjmw]

Hello, I have a HPI RS4 MT with gear diffs. I would like to convert it to ball diffs front and rear but do not want to pay the prices asked for on ebay for the appropriate diffs. Does anyone know whether it is possible to buy parts to build up a ball diff for the MT? Would it just need to be 39T with correct dimension balls, and joint hubs and other parts eg shims etc? This is the only HPI I have owned so do not know whether the Pro 2 ball diffs for example would be appropriate. As a 4wd truck I think it is good but could be even better. If anyone knows it would be great to here your thoughts on this. Thanks Rich