Happy, you gotta post a video of that supercharger madness. I'm not even a little jealous. I'M A LOT JEALOUS! Plus I would really like to see those shift points, tach and all. Nick brings up a good point about the 6 speed swap with the t/c in the mix and adding xdrive logic. It was my understanding that the 5speed and 6 speed were interchangeable, but I could be wrong.

As far as a diff swap, that can easily be done. My wife's X3 has the 3.64 gearing in the diff, and similar tranny ratios and it's awesome. Combined with 6th gear on the highway, mpgs are great. 80 mph is about 3k rpm if I remember right. That taller gearing gives you some more gear to grab and really feel the power swell as you climb in rpm's. Coupled with a supercharger would be nothing short of intoxicating.

What I've done only makes sense (if at all) if we're takling about V8 engines.

The GS6-X53 box of 6-speed manual X5 won't fit - it has bigger TC input shaft and the lenght is also different, due the 5-speed is much shorter.

If you swap the tranny you'll also must swap the TC, which isn't quite logical

Pretty sure the 5- and 6-speed transmissions are physically interchangeable, but I don't know if the 6-speed would give anything more at the top end. I'm pretty sure the 5- and 6-speed have similar ratios in their highest gear, but the intermediate gears are spaced more closely in the 6-speed. Anybody know of a good resource for determining what gear ratios are used in either transmission?

Again - 5-speed and 6-speed manual gearboxes on X5 are not interchangeable!

5-speed box has 1.00:1 ratio in final gear, 6-speed has 0.86.

Not to argue the point -- just curious -- but what about the 6-speeds from the 3.0 X3? Different TC?

X3 6-speed box with ATC400 will only mechanically fit to facelifted X5s ATC500 (both x-dirve), but not to the pre-facelift NV125 (fully mechanical unit, coupled only to 5-speed manuals).

Ok.. Got a chance to test 1st gear today. 10 mph is at 3000 rpm, 27 mph at redline. It's exactly the same as 1st gear for a Honda Civic I previously owned. My X5 has NO tow options at all. Do you think having a tow package would make a difference? 70 mph in 5th was at 3300 rpm. So, if 6th gear put me at 2850 rpm at 70 mph, I would be super satisfied!! One can only dream.. LoL.. Green Dragon and Ricky Bobby, I will try and figure out how to post video ASAP. I am new to message boards, but I had to be a part of the E53 Manual board!!

Happy, from fading memory the final drive of all 5 speed manual cars is ~4.10
There really was no official 'tow pkg' in terms of BMW putting in a diff rear drive ratio; all the 5 speed manual trans cars, regardless of MY had the same trans ratios and final drive gear ratio.

Your speed/rpms in first are consistent with what I see. The redline comes up in a heartbeat, very short time/distance, vs my m'cycles and Vette, lol!
GL, mD

Those speed/rpm figures are exactly what I see on mine; must be the 4:10 diffs on yours as well. That Honda you had must've been a stump-puller! ;)

Add me to the 3 pedal list.

My name is Madison and I just snagged this ultra clean Alpine/Truffle Brown 2005 X5 6 Speed. 122,000 miles with black headliner, pano roof in Houston. Im flying out there and driving it home to Metro Detroit.

http://img.photobucket.com/albums/v4...ps2a5892c2.jpg

http://img.photobucket.com/albums/v4...ps90521359.jpg

http://img.photobucket.com/albums/v4...ps152f3c02.jpg

http://img.photobucket.com/albums/v4...psbacb7794.jpg

http://img.photobucket.com/albums/v4...ps8df220d1.jpg