Quattro/AWD clarification

[TheAvgBear]

So my allroad is the first all wheel drive vehicle I have owned. I have researched the quattro system and generally understand what is going on. I am fairly mechanically inclined, and have been working on the car lately. I have the front end up on jack-stands (so the rear tires are on the ground). Last night I was replacing the axles, and in the process I noticed that both axles spin, even though the transmission is in park? Is this supposed to happen? The vehicle and transmission drove and felt fine when I pulled it into the garage.. So what is going on that allows this? And since it is awd, shouldn't spinning the front axles make the driveshaft and therefore the rear axles/wheels spin as well? If I had the entire vehicle up on 4 jack-stands and spun one wheel, would all four wheels spin? Since I am able to spin the front axles with it in park, what would cause the vehicle to lock and not roll if put into park on a slope or hill? Thanks for any help/info anyone has for me, been scratching my head at this since last night.

[toms73novass]

We have a torsion differential in the tail of the transmission that deals with biasing the drive line. The front and rear diffs are open. If you turn any wheel while another is off the ground or car is in neutral the wheel will spin easily.

[OGBULLYLOCDAWG]

For the fronts, if you spin the passenger side clockwise while in park, the drivers side goes counter-clockwise and vice versa, I guess they "lock" in park by working against each other.

This is all assuming nothing is wrong with my car lol.

[moyenecorniche]

You are equating Audi quattro system with domestic suv / pickup 4x4 system. In the domestic you have a front transfer case and an on or off 4x4 system which is not adaptable to feedback from each wheel as to traction coefficient. Furthermore from the transfer case / transmission you have two centrally located driveshafts one for the rear wheels and one for the front wheels. You will also or should notice that when in an arc, the inside wheel of either front or rear is provided with equal force which means that since the outside wheel is traveling in a longer arc, the inside wheels are forced to spin as fast thus lose traction. Long story short, basically its an obsolete system. ( there has been some improvement but its still a poor system when in snow to dry to wet to icy road surface which doesn't adapt underway.

Quattro is 4 driveshafts, each wheel is entirely controlled by various factors of arc, traction, power, all by the ECU and various sensors. It is a constant awd system but is rear biased.
In your Allroad the system functions differently than in my S4 but it is basically the same.
Just having the car jacked up will allow the front wheels to spin but the rear won't. The locking system is in your transmission and therefore affects rear wheels in a parked mode.
NO ... Again you are thinking of 4x4 which is totally mechanical ( gears and pinions are either engaged or not ) Audi Quattro is 4 drive shafts 2 front and 2 rear in their own transfer case. Not a single centrally located driveshaft splitting into a rear and a front differential.

Simple explanation but Quattro is really quite complex, search and there should be threads explaining the system in great detail.