I was wondering if you know in what e39 is the quickest steering ratio and which one is the strongest?
I am not talking about the m5 since it has a steering box, not a rack. I am looking for a rack.
Can you help me out?
What is it you are trying to do? Sounds like you are trying to put an E39 steering rack into a [insert name of car here]. If you are trying to put a rack into an M5, my understanding is that it won't fit. So if you give more details about the project, people may be able to help more.
There were no 8 cylinder factory E39s with a steering rack, so you're going to have to look to the 6 cylinder cars. It has been done before - one example is a guy over on Bimmerforums that pulled the well ventilated S62 out of his M5 (along with subframe), and replaced it with a steering rack and entire aluminum 6 cylinder subframe. If you swap over the whole subframe (assuming the E39 and E31 V8 subframes are interchangeable), it should bolt up, but those are always famous last words. The upside is that your new steering rack is already mounted to your (lighter) aluminum subframe in the E31 - however, the motor mounts are placed for a 6 cylinder. I don't know what motor you're using, but if you're swapping subframes, you shouldn't have an issue fabbing up some new motor mounts to hold (I'm guessing?) an S62 in place.