its a katana rtr .27, the center diff is the problem. i took it apart and grease in it and also 1 shim was missing. i drive the car hard so your probably right. should there be a shim for each gear? the book i have shows shims on all the gears. somebody over looked something at the factory.must of been made on a friday. so do u think some new gears and diff oil will do it?