I have 1 more question, it is about my 835 (upgraded from 02 spec).....which 2-speed and centax can I use beside the Centax 1...? I kinda think the 710 gear box MIGHT NOT work because the weight of the whole car might damaged the 0.8 pitch gears....but will 835 2-speed (same as the 705) work with the Centax 3? I heard someone said they are different.....and does not work. Will the 2-speed gear box of 705 work with the centax 3 with the centax 2 pinion gears....? Thanks