Originally Posted by Artz 330
My mom and i both picked up e90s about a month ago, Mine is a 6 speed 330i and hers is a 330Xi Automatic. I did a diff swap in my 330Ci and loved it. I am thinking about taking my moms car for the day and swapping My 3.15 into her car and taking her 3.64 and putting it to my car. I wonder how much slower her car would be with a 3.15... at lease she will get better gas mileage. Will this affect the X drive taking her diff or no? anyone?
Thatīs a good recipe for trouble
You can put her diff in your car allright.
But put yours in her car and all hell will brake loose. Sheīll have a different final drive on the rear wheels than the front which means the central diff will be running unequal speeds at the two outputs, will wear like hell, the X-Drive electronics will be in "WTF-mode", the brakes will be applied by X-drive to slow down the "slipping" wheels etc.
In short, thatīs one helluva expensive mod.
Besides, the diffs will probably not fit anyway. You might have to shorten drive shafts etc. to make them fit.