thanks Simon. Its funny how you trust the validity of theory until its your own gearbox and then you start to go 'wait, that better be right that the bolt torque alone will hold it all together!'. The Kaaz instructions that came with the diff only mention torque specs for Honda and Mitsu Evo applications. I'll have to contact them re torque specs for the VW fitments cos obviously now I'll have to be 100 percent correct or I'll always be driving the thing going 'whats that noise', 'whats that vibration' and head ****ing myself that it wasn't done right.
There's two other things playing on my mind. Firstly the fact that if I do go to an 02J 114mm crown wheel and pinion, that I can change final drive. Secondly that I believe that if you fit a 5th gear from a TDi box you can get a proper overdrive gear for the freeway rather than pulling too high revs at 110kph.
Apparently the JDB box I'm building has the same ratios 1st,2nd, 3rd,4th inc reverse as the earlier HWY box I'm running now. So I could go to a punchier final drive but extend 5th so I can still get down a freeway to get to the events. Not sure if that will make 1st un-useably short though as its a split second gear already, but then again with the better diff I may be actually able to lay into it with that gear off the line rather than short shifting out of it. And if I do move away from a k03s to a K03 hybrid (inevitable), a snappier final drive could help driveability and keep me out of lag holes. thinking muchly..