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Question About Diff-Lock Functionality

 
Old 01-08-2014, 11:25 AM
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RacerX5
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Default Question About Diff-Lock Functionality

I am borrowing a 2006 Cayenne S from my mechanic, (with the thought of buying the car). Unfortunately, it has no owner's manual. I am uncertain that the 4WD control is functioning normally. When I push the dial forward, (while in neutral), first the center LED lights, then if I hold it longer, the forward LED lights. If I pull the selector back, these LEDs go out.

First, I would like to know what exactly the system does, I presume center diff lock, and I am told the center LED is gear reduction, but I really don't know. From the look of the light design, it would almost appear that it is front diff lock, center diff lock, and rear diff lock, but that would be too much to hope for, so I presume that's not correct.

Second, what does the rear most indicator mean? (Mine does not light at all...I presume that is not a good thing.) Is it supposed to be lit all the time indicating highway mode?
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Old 01-08-2014, 11:43 AM
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Here is the owners manual.
http://www.porsche.com/all/media/pdf...yenne_pcna.pdf

Page 177. Looks like the manual is for a 957 based on the graphic of the selector but the functionality should be the same.
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Old 01-08-2014, 12:24 PM
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Originally Posted by endless_corners View Post
Here is the owners manual.
http://www.porsche.com/all/media/pdf...yenne_pcna.pdf

Page 177. Looks like the manual is for a 957 based on the graphic of the selector but the functionality should be the same.
Thank you very much for that. OK, now I understand the functionality.

But I still get no light for the locking rear diff. Is it possible that I have a vehicle without a locking rear diff? Was it an option or standard equipment? There is definitely a third indicator on the 4WD selector, (that does not light up). And no message regarding rear diff comes up on the dash either. It does properly shift into low range and indicate when the center diff is locked.
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Old 01-08-2014, 12:34 PM
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Yes you dont have a locking rear diff.....it was an option....mine is the same.....centre is diff lock and forward is front diff lock...there is no rear diff lock unless it was ordered.
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Old 01-08-2014, 12:37 PM
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and when you play with the switches also look around in the console.....it says reduction on and the car with the centre light comes on.... and then says LONG LOCK ON and it displays a car with a front diff lock illuminated.
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Old 01-08-2014, 12:37 PM
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Locking rear diff is rare. Comes with the advanced offroad package.
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Old 01-08-2014, 12:41 PM
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The offroad pkg/ rear locker is rare indeed; I've never seen one in the flesh.
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Old 01-08-2014, 01:09 PM
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Originally Posted by virkdoc View Post
and when you play with the switches also look around in the console.....it says reduction on and the car with the centre light comes on.... and then says LONG LOCK ON and it displays a car with a front diff lock illuminated.
Yes it does that.

So I guess it does NOT have the locking rear diff. Many thanks to all those who have replied.
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Old 01-08-2014, 01:14 PM
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Too bad you can't lock the center diff in high range. I have that function in my 2004 4Runner, and it's really nice in deep snow. In the 4Runner, that same locking center diff button also disables the stability control at the same time. I use this feature on snowy roads quite a bit, and the stability control does not let you spin wheels, which many times you need to do to go at all. But the car really is very stable with this on.

Looks like in the Cayenne, you can only lock the center diff in low range.
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Old 01-08-2014, 01:22 PM
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Originally Posted by virkdoc View Post
Yes you dont have a locking rear diff.....it was an option....mine is the same.....centre is diff lock and forward is front diff lock...there is no rear diff lock unless it was ordered.
From what I read here and in the manual, it is NOT locking the front diff. Center light indicates gear reduction, (low range), and front light is locking the center diff.

Keep in mind that the traction control system acts in a similar way to limited slips, or locking diffs...just not as well, or as costly. If your right rear wheel starts spinning, it will apply the brakes to only that wheel, in effect sending power to the left rear wheel. When the center diff is locked, it will also equalize power sent to the front and rear axles. A locking rear diff will equalize traction to both rear wheels, without applying the brakes and potentially slowing your forward progress, (a very good thing off-road). When all 4 wheels are slipping, you don't go anywhere until you turn off the traction control, (the traction control can apply the brakes to all four slipping wheels at once). But an electric locking diff is a very expensive item, so I can see why few Cayennes would have them. Not too many of these cars will see dirt anyway.
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Old 01-08-2014, 01:45 PM
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ok I need help too....so what happens if the low range is on? I mean in what condition do I use it? And in what condition do I use the centre diff lock?
So ther eis a centre diff lock, a front diff lock and a rear diff lock??
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Old 01-08-2014, 02:14 PM
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Originally Posted by virkdoc View Post
ok I need help too....so what happens if the low range is on? I mean in what condition do I use it? And in what condition do I use the centre diff lock?
So ther eis a centre diff lock, a front diff lock and a rear diff lock??
No front diff lock. And from what's posted above, in all likelihood, no rear diff lock either.

Low range is for off-road only. Like on the beach or a rocky trail. Seems to me you would want the center diff locked in all those situations, I can't think of a situation where you would want the vehicle in gear reduction mode, but NOT want the center diff locked. You may not need the center diff locked, but I can't think of a downside to having it locked off-road.
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Old 01-08-2014, 02:55 PM
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If you're in a situation where traction generally is poor,e.g., glare ice, deep snow, sand, deep mud, you want the center diff locked. Low range is for off-pavement, crazy steep grades or stump pulling. I can't think of any situation for low range on a normal graded road.
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Old 01-08-2014, 03:18 PM
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Originally Posted by DWC in Sedona View Post
If you're in a situation where traction generally is poor,e.g., glare ice, deep snow, sand, deep mud, you want the center diff locked. Low range is for off-pavement, crazy steep grades or stump pulling. I can't think of any situation for low range on a normal graded road.
I agree. But with the Cayenne, you can't lock the center diff without being in low range. Which makes no sense to me, but that's the way the car is designed.
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Old 01-08-2014, 04:52 PM
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Originally Posted by RacerX5 View Post
I agree. But with the Cayenne, you can't lock the center diff without being in low range. Which makes no sense to me, but that's the way the car is designed.
Correct...first comes low range, then locked diff. I've use low range in the Cayenne only once to try it a year ago and forgot. I was projecting from my previous 4WDs. I also agree the sequence should be reversed.
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