Gearbox and Diff Options - E39 523i

[justlikemusic]

Ok I have a '97 523i and currently have a few bits and pieces being done to it:

Cold Air Intake
Thermofan (Engine Fan delete)
Traction control throttle body delete
Remove rear catalyster and last muffler replaced with Lukey and twin chrome tips

I also am changing the CCV, cleaned the ICV and intake manifold. Ultrasonic clean on the injectors and when it's back together running again it will get the fuel, water, engine flush treatment with new fluids.


Now I have to do something about the gearbox and the diff.
I want a higher diff ratio... I can do 120km/h (75mph) in 2nd gear, and by that time I'm already going faster than any speed limit in my country. Now with the intake and exhaust I am sure it will have more up top and rev a little more. I want to be able to hit third at least by 100km/h if possible (60mph)... is there any diff's I can just interchange with this vehicle from another one?

Also is there anything I can do to harden up the changes in my gearbox? I haven't checked the fluid level and I suspect that there may have been some fluid leakage from there over the years and it needs a top-up or something. I will have to check this since the car is off the road with engine work being done and full ICE install at the moment.

[justlikemusic]

Ok from what I have read so far...

The 528i 4 speed automatic diffs are 4.10 ratio, however my car is a '96 build, '97 registered E39 and I haven't seen any diff swaps from cars older than 1999 yet... still reading -.-