What is "AUTO" mode really, vs. the 2WD and 4x4???

The Gas and Diesel Engines - VQ40De, VK56DE, YD25DDTi, V9X, Transmission, Transfer Case, Oil, Differentials, Axles, Exhaust...

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What do you leave your transfer case set to every day?

2WD always
109
75%
AUTO always
25
17%
4H always, I'm hard core.
1
1%
I wish I had a choice :-(
10
7%
 
Total votes: 145

edward
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fwd or awd?

Postby edward » Thu Nov 06, 2014 7:13 pm

When i first got my 2013 path, i drove in fwd mode for about 3 days.I got tired of spinning the front tires at every other stop.using auto mode now, took care of that.guess i have a heaver foot than most people.


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Clay350
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Postby Clay350 » Tue Nov 18, 2014 8:20 am

Auto mode is nice but it doesnt seem like a good idea to have it on if you were on pavement moving at speed. That kind of defeats the purpose for me being able to have more traction on roads that are snowy and icy part of the time. Am I wrong on this? I can feel the difference at 50mph on normal roads?

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smj999smj
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Postby smj999smj » Tue Nov 18, 2014 1:04 pm

Clay350 wrote:Auto mode is nice but it doesnt seem like a good idea to have it on if you were on pavement moving at speed. That kind of defeats the purpose for me being able to have more traction on roads that are snowy and icy part of the time. Am I wrong on this? I can feel the difference at 50mph on normal roads?
If you are in AUTO mode on pavement at high speed, you are essentially in 2WD unless a slip occurs. The transfer case uses a wet clutch and can apply power at varying levels and as needed to obtain proper traction. It can also anticipate a slip based on speed and throttle position. If you are doing normal driving on dry pavement, you shouldn't feel any difference between 2WD or AWD. I don't in my 06 LE and I use AUTO all the time.

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Clay350
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Postby Clay350 » Wed Nov 19, 2014 7:20 am

smj999smj wrote:
Clay350 wrote:Auto mode is nice but it doesnt seem like a good idea to have it on if you were on pavement moving at speed. That kind of defeats the purpose for me being able to have more traction on roads that are snowy and icy part of the time. Am I wrong on this? I can feel the difference at 50mph on normal roads?
If you are in AUTO mode on pavement at high speed, you are essentially in 2WD unless a slip occurs. The transfer case uses a wet clutch and can apply power at varying levels and as needed to obtain proper traction. It can also anticipate a slip based on speed and throttle position. If you are doing normal driving on dry pavement, you shouldn't feel any difference between 2WD or AWD. I don't in my 06 LE and I use AUTO all the time.
See I thought the same thing but thats not the case. If im in auto on dry road I feel the front engaged. Many people have said the same. Granted at a lower coupling rate. 4wd just isnt meant for pavement at high speeds regardless of the coupling. Am I wrong here? This is not a true AWD setup just a fancy 4wd configuration.

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smj999smj
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Postby smj999smj » Wed Nov 19, 2014 10:44 am

If you go all the way to the first post, it'll explain how it works. The Nissan AUTO-mode system is similar to GM's Smart Trak II system in that it drives in RWD until slip is detected and also, at least in the Nissan's case, anticipates a slip based on certain inputs. These are different from the way GM's first Smart Trak system worked, whereas there was always at least some power applied to the front wheels at all times and that amount would be increased, as needed in a slip condition. The phrase all-wheel drive is open to debate as to how it should work. R51's use open diffs front and rear with electronic limited slip that uses the ABS system to brake a free-spinning wheel to allow power to go to the wheel with the traction, so, there is never a time when all four wheels are working equally as drive wheels at the same time, even in regular four wheel drive mode.

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leadpig
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Postby leadpig » Wed Nov 19, 2014 12:51 pm

smj999smj wrote:R51's use open diffs front and rear with electronic limited slip that uses the ABS system to brake a free-spinning wheel to allow power to go to the wheel with the traction, so, there is never a time when all four wheels are working equally as drive wheels at the same time, even in regular four wheel drive mode.
So, for those of us slumming it without the auto feature, what is the difference there? When 4wd is engaged I was figuring the center diff was locked with a 50/50 split (hence the speed limits) so I never engage unless I'm on something slippery and disengage if, for example, the road is only partially snow covered. Am I wrong? If so how should I deal with mixed surfaces?

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smj999smj
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Postby smj999smj » Wed Nov 19, 2014 1:36 pm

Even with the AUTO-mode trans, there is an option for 4-HI and 4-LO, just like the standard transfer case. In the 4-HI and 4-LO mode, it does lock the transfer case, as you suggest. 4-Hi is recommended for rocky, sandy or snow covered roads and the speed should not exceed 62 MPH (31 MPH for 4-LO). 4-HI and 4-LO should NOT be used on hard, dry surfaces. As far as "mixed," common sense should dictate what mode the transfer case should be in. By "mixed," I'm assuming you mean snow in some areas of the road in no snow in other parts, but even under those circumstances, the parts with no snow will still usually be wet, so being in 4-wheel drive will be fine. The advantage of the AUTO-mode is you can leave it in AUTO all the time and it takes a lot of the "common sense" out of the issue for most scenarios, as it will shift itself between 2WD and 4WD.

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leadpig
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Postby leadpig » Thu Nov 20, 2014 8:11 am

Good, thanks for the explanation.

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viking84
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Postby viking84 » Fri Feb 27, 2015 1:48 pm

A bit of thread resurrection - the Scandinavian spec V6 Diesel Pathfinders don't even have the 2WD setting, so we have to drive in Auto all the time. Would have liked to be able to select 2WD for some hooliganism in the snow, but for all other purposes Auto is great :wink:

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car_bore
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Postby car_bore » Sun Jul 26, 2015 10:50 am

Would there be any differences in gas consumption if I choose AUTO vs. 2wd?

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smj999smj
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Postby smj999smj » Mon Jul 27, 2015 4:37 pm

car_bore wrote:Would there be any differences in gas consumption if I choose AUTO vs. 2wd?
The owner's manual says use 2WD for maximum gas mileage, but I've tried both and still got the same gas mileage, around 17.5 mpg combined.

BCpathy
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dry/wet pavement

Postby BCpathy » Fri Oct 23, 2015 12:40 am

What exactly is the definition of "dry" pavement.

I mean, if the road is just a little wet from a drizzle of rain, good tires still maintain almost 100% traction. So do studded tyres on a light snow cover, given there is no ice underneth.

i don't think that you risk drivetrain damage in all these cases. It's much more about the differing speed of the left and right front wheel.

Therefore I believe it to be just fine to drive 4hi on "dry" pavement, if one wants to. It is unnecessary and pointless,nbut won't damage anything.
As long as you don't go into sharp turns. After all, the revs per min are almost identical for left and fight front wheel, when driving relatively straight. A windy road might be a problem, but a "straight" country road should be fine.
other than, you would also damage the driveline in every sutuation, where your tires maintain exellent grip.

I think it is way more important to make sure that the driveline fluids are refreshed as required and that the 4WD stays lubricated. Means driving it on a gravel road or something like that in 4hi every now and then.

one thing that does bother me about the drivetrain of the pathy, is that the u-joints are non greasable ones. Thats a possible/probable cause for drivetrain damage.
I'll be replacing them soon. But thats another topic.

correct me if I'm wrong.

DavidUk11
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Postby DavidUk11 » Sun Nov 08, 2015 12:17 pm

As I understand it from this thread, the front and rear differentials don't "Lock" is that correct only the centre diff I us that correct?

I want to create an override so that I can use Lo ratio at low speed without any diffs locked. Possible or not do people think?

I will have a look at the workshop manual.

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smj999smj
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Postby smj999smj » Sun Nov 08, 2015 1:36 pm

DavidUk11 wrote:As I understand it from this thread, the front and rear differentials don't "Lock" is that correct only the centre diff I us that correct?

I want to create an override so that I can use Lo ratio at low speed without any diffs locked. Possible or not do people think?

I will have a look at the workshop manual.
I'm not sure how they are in the UK, but the North American models have open differentials front and rear. They have "electronic limited slip," where the vehicle used the ABS system to apply brakes on the slipping wheel so the traction wheel gets more power. It works okay...and I noticed a number of other manufacturers, including Mercedes Benz, use the system in some of their vehicles.

DavidUk11
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Postby DavidUk11 » Sun Nov 08, 2015 1:52 pm

With my car, in 4wd Hi or Lo there appears to be a lot of stress on the transmission doing the right manoeuvres I have to do shifting my boat on and off my drive (Hard pavement).

I will have to have a look at the front and rear diffs and see if there is is anything that might lock them. If it is system using the brakes that is not a problem as the wheels do not slip on the tarmac. I am wondering if putting a switch in the power to the electric oil pump might free up the centre diff and make things easier. I will have a re-read of this thread which is very informative thanks.


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