Why is this? Diff/driveline question

[mcgillaguddy]

Today I was out swapping my wheels back to the original 15" weaves and I found something to be a bit odd...

I was able to spin the left/right rear wheels independent of each other (the wheel opposite did not turn) and then I found the same was true for the front. - Should they have not spun together?

I would have assumed that the wheels would have spun together, in pairs at the very least - as they did in both my last 325is and my 535is e28..

Am I being a dunce or is this weird? Is there something I am missing?

[TehRaydarlover]

Was it really hard to turn the wheels individually? I think they should be able to turn independently but it should be really hard because your trying to turn it against your vc's. If it wasn't hard both your vc's might be shot.

[The Dark Side of Will]

Sounds like both your transfer case and rear end VC's are shot.

[mcgillaguddy]

The fronts were somewhat easier than the rear. I had the rear of the car in the air, with neither tire touching the ground and they still did not spin together.

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[mcgillaguddy]

I'm assuming I should be sourcing a new rear diff as well as a new TC?
Also, rear diff must have to remain the same ratio in order to allow front/rear to spin together?

I'm sure I can find out that info via searching...

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[Ether-D]

Also, rear diff must have to remain the same ratio in order to allow front/rear to spin together?

Absolutely.

[nomansland92]

The front is a open differential, therefor if you spin one side the other will most likely spin backwards. The rear on the other hand is a 90% vc lsd. So spinning one should spin the other. Have someone hold one side and try to spin the other, it should only allow a 10% difference before they become locked. The best way to test the transfer case is the jack test.

[mcgillaguddy]

Thanks for the info, I'll try it out. I failed the jack test, so I knew the transfer case was bad already but I did not expect to be able to spin tires completely independently.

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[nando]

you can turn the rear VC, depending on condition and how much leverage you have. it also depends on if it's in gear or not, etc.

I think the rear VC is NLA, unfortunately.

[The Dark Side of Will]

you can turn the rear VC, depending on condition and how much leverage you have. it also depends on if it's in gear or not, etc.

I think the rear VC is NLA, unfortunately.

I have a blown TC VC and a good rear VC in my car.
My experience when replacing my fuel tank was this:

-With the rear end up, the front end down and the trans out of gear, turning one rear wheel resulted in the other rear wheel turning the same direction and the driveshaft turning.
-With the rear end up, the front end down and the trans in first gear, turning one rear wheel was possible, but it was VERY stiff. The other wheel turned the opposite direction and the driveshaft did not turn.

These two factors allowed me to diagnose good rear VC and bad TC VC.

The way it *should* work:
-With the rear end up, the front end down and the trans out of gear, turning one rear wheel should be quite stiff. The other wheel will turn the opposite direction, but may turn more slowly. The driveshaft may turn slowly also. You're establishing a speed difference across both VC's, but they are in "parallel" so the resistance is less than either one by itself.
-With the rear end up, the front end down and the trans in first gear, turning one rear wheel should be stiffer than with the trans out of gear. This is because you are only turning the rear VC, and not putting the TC in parallel with it.

-With the front end up and the rear end down, turning a front wheel should result in that wheel turning freely and the other wheel turning freely in the opposite direction. If the driveshaft turns while the trans it out of gear, the TC VC is bad.