hi all/neil...well its like this if the 18t gear is around 20mm daim (at the large end) then its p.c.d will be around 18mm, p.c.d is around halfway between the top and bottom of the tooth, so to find the mod we divide the number of teeth by the p.c.d, so no prizes for coming up with the answer of 1 .

would be good to bullet proof the diffs but i have seen others who have mm combo in there txt-1 so must be ok as long as you're not landing big air jumps with the throttle open.