Well with any transmission or engine swap that isn't stock for your car its usually a somewhat daunting task. I have done Auto to Manual swaps before on different types of cars and honestly they have never been a cake walk. You usually will walk away from the project cursing on more then one occasion.
I don't recommend these projects for for the light duty DIYer unless you can have the car sit to the side for about a month. I'm not sure how BMW ECU and TCU work out I know on Subarus there are separate units but on Hondas for example they are the same unit. Transmission themselves if your lucky are generally the same dimensions only the ATs are usually heavier but you have to concern your self with loads of other things like; Gear selector removal and Manual linkage installment, Manual pedal installment (Yes you have to remove all of the old AT pedals one of the biggest pains in this swap.) If one tranny is longer then the other a drive shaft swap is in the cards, Possibly rear end with axles, Master and Slave cylinder installation and bleed, ECU swap (not always necessary but your car will run better knowing what Tranny your using fuel maps are generally different), rewiring your tranny to your chassis (your Ecu needs to know whats going on with the Tranny not to mention backup light are nice too), Torque converter and flex plate removal, Flywheel and clutch system installment (recommend replacing the rear main crank seal at that time too)... I might be missing some things.
This is a hard job and I would only recommended doing it if you had enough down time for your car. I also recommend getting some people in on your swap I've always needed help with any engine or tranny swap. you gotta remember that auto tranny weighs almost 200lbs Your going to need help with moving it!
1986 BMW 325e
1990 Mazda Miata MX-5
1981 Honda C70 Passport
Anything with an internal combustion engine.
Last edited by Jedz123; 01-06-2009 at 11:59 AM.