strength of a S6 manual box vs a S4 & S5 box
 

how strong is a S6 gearbox compared to a 2nd Gen box? any differnt ratios or any thing like that?

S6 and T2 gearbox has the same internals.
Casing is different though, one might be stronger than the other. I dunno

Gear ratios here:
http://mrmazda.no-ip.com/tranchrt.txt