Hi swathdiver,  
   I'm urging to know really[:-]!!! Just now I 've told him and still he also wants to try by using metal gearboxes 3:1,metal tracks&sprockets.
I told him that for the sake of knowledge try it and if any thing happen that's a cost of learning(  purchase one more M41A3 for spare)
Do you think that metal gearboxes will last?</p>