I've had a good old forum and internet search on fitting an M5 steering box into my 540i including some useful information from Steve Wright (built an E39 M5 Touring). He has the M5 box on the 540i steering components. However he also has the full M5 loom so has been able to connect up the servotronic.
I have sourced an M5 box at reasonable cost from a BMW breakers.
My 540i does not have servotronic. If I simply fit the M5 box in with no servotronics connected can anybody tell me what would happen apart from a welcome reduction in turns lock to lock?
I assume it would probably run at the maximum heaviness (equivalent to your M button being pushed). Now my 540i is fairly heavy at all times on the steering so I can live with that happily as long as it's no heavier. If it ran full light all the time I wouldn't be as happy.
So, the specific questions are:
1) Does anybody know if it will run light or heavy?
2) If you leave your M button on all day in your M5 is it still a reasonable weighting to park and manoeuvre?
3) Is there anything else I should have considered?