4x4 doubt
 

I have a E53 3.0D 2002(not xdrive), and Today I replacing the brake pads(front/rear).As the car was lift up, and when i spin the behind weel, the front weels dont moved.
If it is always 4x4, why dont move it together???? :confused::confused::confused:

Open diff in the rear.

Can you explain me whith more detail, please.

All the differentials are open. If you spin one rear wheel, the other can just spin the opposite direction, if the drive shaft is fixed. If you spin both rear wheels the diff in the transfer case is open anyway.

It isn't commonly referred to as 4wd, but rather as awd, meaning the front and rear are not locked together.

The way that AWD vehicles work are all over the internet...and you'd probably get a better & well written explanation versus us trying to fill in the blanks...not knowing what you already know or don't know.

To explain how BMWs original AWD X5s work would be redundant when the info is already out there. And with much respect...it would take a lot of info to get you up to speed if your perception is that turning the wheels on the rear axle (behind wheels) should also turn the front axle (ahead wheels?) ... since the X5 of your era uses a center differential (not locked) which uses (I believe) a 60/40 power split as a default driveline. :)

Here's an example of the type of information out on the internet that may help you understand better: All Wheel Drive Explained | awd cars, 4x4 vehicles, 4wd trucks, 4motion, quattro, xDrive, SH-AWD, Haldex, Torsen, wiki - How it works

Read the article at the link above to educate yourself on the various AWD systems...then if you have more questions...feel free to ask for more clarification. :)

Thanks for your response and knowledge.
I suppose then, that it is normal when the car is on a lift, if I rotate a wheel on hand, and the wheels on the other axle does not rotate. I´m right?

You are right. :) The wheels are not LOCKED all together all the time...if they were, the transmissions would be blowing up all over the place because wheels don't rotate at the same speed or travel the same distance left to right or axle to axle unless you are driving in a straight line.

I found a post here on the forum, with some photos, but I still do not understand where is the clutch, to make the two TRANSMISSIONS not run on simultaneously.
It seems to me, that works permanently???

It's not a clutch - it's a planetary gear set, that means your front and rear axles would behave as 2 wheels connected to an open differential, if the axle diffs were locked.

As allready said - all the 3 diffs in X5 are open, not locked.

Otherwise, normally you always have enough traction on each whell and it's all time 4x4. If you're in snow or in sand and only one wheel won't have any traction at all, the only wheel without traction will spin useless.

See this thread, particularly post #13, for an explanation of the transfer case functioning.

http://www.xoutpost.com/bmw-sav-foru...lower-rpm.html