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Question About Diff-Lock Functionality

 
Old 01-08-2014, 05:48 PM
  #16  
RacerX5
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Originally Posted by DWC in Sedona View Post
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.
I have 3 other SUVs, and they all work differently.

The X5 has no low range, and has a clutch system that directs power front to rear. Has a little actuator motor that shifts power fr/rear when the computer says so, with a ****ty PLASTIC gear to run it, (notorious failure point of all BMW AWD systems). Open diffs front and rear. No one in their right mind would take an X5 off-road. 315mm 35 series tires won't help either.

My Jeep Grand Cherokee, (lifted 6") has had the viscous couple AWD transfer case (249) replaced with one the locks up in 4WD (242). Now has a 2WD option. I have open diffs in that too, but it has climbed dirt trails you could not even begin to walk up. 33" mud tires help that process, (barely streetable). I do have a lunchbox locker that will soon go in the rear axle.

My 2004 4Runner has a 2WD High, 4WD High 4WD Low transfer case. Plus descent control. You can lock the center diff and turn off the stability/traction control in 4WD high. lt's all electronic, so you can switch anything except selecting low range on the fly. The traction control does work pretty well off-road.

All these off road bells and whistles do little for you on the road, but a locking center diff is nice in deep snow. But once it gets to over 6" deep, you might need low range anyway.

So how fast can a Cayenne S go in Low range?????
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Old 01-08-2014, 07:41 PM
  #17  
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I can't believe I'm typing this, but can someone translate what a locking differential means, in English? I'm not an off-roader, but I have used the rocker switch in some ugly snow on the way to Tahoe once. I just know the more I pushed it forward, the better the traction got. But I have no idea what any of this actually translates to, in mechanical terms (I know what a differential is, but I thought I only had front/rear)... need a quick tutorial. Thanks.
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Old 01-08-2014, 07:54 PM
  #18  
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Originally Posted by RacerX5 View Post
All these off road bells and whistles do little for you on the road, but a locking center diff is nice in deep snow. But once it gets to over 6" deep, you might need low range anyway.
I've had 2 Mitsu Monteros and an H3. The 4WD on the Monteros operated like your 4Runner but with a viscous coupling ctr diff; the H3 had locking center diff for 4H and 4L, rear locker and a super low range. I'd have kept the H3 but it was grossly underpowered on the road with the 5 cyl.

Don't know how fast the Cayenne will go in low; but a Turbo is probably the fastest 0-10 on wheels!!.
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Old 01-08-2014, 09:50 PM
  #19  
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Originally Posted by seankrider View Post
I can't believe I'm typing this, but can someone translate what a locking differential means, in English? I'm not an off-roader, but I have used the rocker switch in some ugly snow on the way to Tahoe once. I just know the more I pushed it forward, the better the traction got. But I have no idea what any of this actually translates to, in mechanical terms (I know what a differential is, but I thought I only had front/rear)... need a quick tutorial. Thanks.
The locking "center diff" in the Cayenne is really within the transfer case. Probably not a really accurate term, as one usually refers to a differential as within an axle; but a transfer case can also allow for a difference in drive shaft output front vs. rear. But it's one of those automotive terms that's sort of stuck.

Under normal condition, the front and rear drive shafts are allowed to get different amounts of power. Some cars allow the front/rear bias to be adjusted with a dial, (a JDM Skyline RE34 for example). Others send deliberately more to the front or rear to determine the handling balance of the car. For example, a Nissan Murano sends most power to the front, and only sends power to the rear if it detects slippage at the front, (which is why they drive like crap). A Porsche Carrera 4 will do exactly the opposite; it sends more power to the rear until it detects slippage at the rear, then sends more to the front. These cars use computer controlled actuators that shift power based on the speed sensors, yaw indicators and a whole boatload of computer parameters to determine the right mix front to rear. Most of these cars shift power with clutches or viscous couplings in the transfer case, but there are some gear and chain driven cases as well. But when the transfer case ("center diff") is locked, the front and rear drive shafts will be forced to run at the same pace.

These computer controlled power shifting systems just tend to get confused when traction is really limited all around, so that's why the Porsche Cayenne and many other 4WD vehicles give the option of locking the center diff in the transfer case.
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Old 01-08-2014, 09:58 PM
  #20  
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And what is low range?
Originally Posted by RacerX5 View Post
The locking "center diff" in the Cayenne is really within the transfer case. Probably not a really accurate term, as one usually refers to a differential as within an axle; but a transfer case can also allow for a difference in drive shaft output front vs. rear. But it's one of those automotive terms that's sort of stuck.

Under normal condition, the front and rear drive shafts are allowed to get different amounts of power. Some cars allow the front/rear bias to be adjusted with a dial, (a JDM Skyline RE34 for example). Others send deliberately more to the front or rear to determine the handling balance of the car. For example, a Nissan Murano sends most power to the front, and only sends power to the rear if it detects slippage at the front, (which is why they drive like crap). A Porsche Carrera 4 will do exactly the opposite; it sends more power to the rear until it detects slippage at the rear, then sends more to the front. These cars use computer controlled actuators that shift power based on the speed sensors, yaw indicators and a whole boatload of computer parameters to determine the right mix front to rear. Most of these cars shift power with clutches or viscous couplings in the transfer case, but there are some gear and chain driven cases as well. But when the transfer case ("center diff") is locked, the front and rear drive shafts will be forced to run at the same pace.

These computer controlled power shifting systems just tend to get confused when traction is really limited all around, so that's why the Porsche Cayenne and many other 4WD vehicles give the option of locking the center diff in the transfer case.
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Old 01-08-2014, 11:13 PM
  #21  
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Originally Posted by seankrider View Post
I can't believe I'm typing this, but can someone translate what a locking differential means, in English? I'm not an off-roader, but I have used the rocker switch in some ugly snow on the way to Tahoe once. I just know the more I pushed it forward, the better the traction got. But I have no idea what any of this actually translates to, in mechanical terms (I know what a differential is, but I thought I only had front/rear)... need a quick tutorial. Thanks.
Search "differentials" on YouTube for videos to explain the different types; open, limited-slip, and locking differentials. Since 4WD links the front and rear axles, there must be a differential with full-time 4WD. Old school 4WD without a center diff could break an axle if engaged on dry pavement; that's what locking hubs prevented.
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Old 01-09-2014, 12:01 AM
  #22  
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Originally Posted by virkdoc View Post
And what is low range?
Just a selectable lower gear ratio in the transfer case. Again, not something you'd use on the road. One of the most critical needs for low gearing when off-roading is when going down steep grades. Use of the brakes can cause you to lose control. Low gearing keeps you going slow enough to maintain control.

Descent control, (look in a Range Rover, modern Jeep GC, or Toyota 4Runner) is a computerized wizard that allow the ABS system to control the brakes going downhill off-road to keep control...but nothing beats a properly lower gear ratio.
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Old 01-09-2014, 11:15 AM
  #23  
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In deep snow its hard to have fun unless you turn PSM off and hit sport mode, then its a blast
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Old 08-02-2017, 10:33 PM
  #24  
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I just bought a 04 Porsche cayenne s. And my wife move the rocker switch and it got stuck and it will only go 2 m/h. I was told to unplug and plug back the car rocker switch, nothing happened and then went to check the battery and the battery was good. It still don't want to work. This is what it says in the screen. Long. Lock off reduction on
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Old 11-06-2017, 08:59 PM
  #25  
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Originally Posted by Adan Fernandez View Post
I just bought a 04 Porsche cayenne s. And my wife move the rocker switch and it got stuck and it will only go 2 m/h. I was told to unplug and plug back the car rocker switch, nothing happened and then went to check the battery and the battery was good. It still don't want to work. This is what it says in the screen. Long. Lock off reduction on
Yeah, you are stuck in low range. If it won't come out, disconnect battery, wait a few minutes and the connect (just the ground will do fine). If this doesn't work you probably have a mechanical issue. Visit a shop or your dealer.
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