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Discussion Starter #1
The other day, in some very heavy rain, I wanted to run with the AWD turned on. I slowed down (ok, stopped) and turned on the AWD (BTW, what a pain that is ... I've not had to do that in a 4WD vehicle before--I could hit 4WD in my 97 Blazer at 100kmh and feel it kick in)....

Anyway, I was on and off snow covered wet and icy roads (did I also mention there was freezing rain? -- Jaak, that was north of Creemore just after Christmas). I noticed that that AWD stayed locked in for about 3 minutes before kicking out.

I tried this several times and it kept dropping out.

Is this normal?

Mike
 

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The AWD system is automatic and you shouldn't need to use the AWD lock unless you're stuck and starting from a stop. Trying to lock the AWD system on mixed pavement like that may cause your transfer case to fail which, by all accounts on this forum, will cause your transmission to fail.

Depending on year, the AWD system will disengage in an effort to protect itself. For 2003/2004 models, the AWD lock disengages at arond 18 mph. For 2005+ models, the AWD lock disengages at 6 mph. The thought is that if you're doing 6 mph, you're not stuck. And if the front tires start slipping, the AWD system will automatically transfer power to the rear.

Bob
 

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Discussion Starter #3
AWD Dropout - 2005 MO

I not sure if I totally agree with you and I fully understand how and when it automatically kicks in.

That being said, I've run with it at 100kmh and it does NOT disengage for about 3 minutes at that speed.

I need to make some calls to Nissan.

Mike
 

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Re: AWD Dropout - 2005 MO

va3mw said:
I not sure if I totally agree with you and I fully understand how and when it automatically kicks in.

That being said, I've run with it at 100kmh and it does NOT disengage for about 3 minutes at that speed.

I need to make some calls to Nissan.

Mike
Just don't mention you have been running it on dry pavement, a sure way to void your warranty! :4:
 

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Discussion Starter #5
Dry Pavement

I doubt it....

Is it written in the owners manual and I've missed it?
 

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Re: AWD Dropout - 2005 MO

va3mw said:
I not sure if I totally agree with you and I fully understand how and when it automatically kicks in.

That being said, I've run with it at 100kmh and it does NOT disengage for about 3 minutes at that speed.

I need to make some calls to Nissan.

Mike
Why are you assuming AWD remained engaged at 100 kmh? Because the AWD light was lit?

If you engage the AWD Lock the AWD light will illuminate. However, once you exceed 10 kmh and if traction is satisfactory the AWD system will disengage . The AWD light will remain illuminated for a period of time.

The following is from the '05 owners manual (Page 5-25) :"LOCK mode will change to AUTO mode when the vehicle is accelerated or the vehicle speed is over approximately 10km/h (6MPH). The AWD LOCK indicator light does not go off. LOCK mode will change to AUTO mode automatically when the vehicle has been driven for a long period at high speed. The AWD LOCK indicator light goes off."

Just because the AWD LOCK light is illuminated it does not mean the rear wheels are engaged.

-njjoe
 

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Discussion Starter #7
Yep

Ah, I stand corrected...

I was just about to post the same thing and correct myself as I just went looking in the owners manual.


Thanks for taking the time to type the entire thing in!

Any mention of the drive pavement issue? Surely the computer must be able to detect this and adjust accordingly.

Mike
 

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The Murano's transfer case/AWD assembly is not meant for 100% duty, so the AWD Lock should not be operated unless you are in constant slip conditions (i.e. unplowed roads or lots of ice). Running the AWD Lock on dry pavement will wear out the AWD components and may lead to premature failure of the system.

I admit though, the vehicle is much more stable with AWD Lock on when the roads are snowy and icy (non plowed). With the automatic AWD, it takes a while to kick in, and sometimes abruptly, which can be a little dangerous on a tight turn, even with VDC (which similarly reacts quite slowly).
 

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From what I understand, if the AWD LOCK is engaged the system acts as if there is a closed differential between the front and rear. It does not allow for slippage and therefor can put undue stress on the driveline when making sharp turns on dry pavement.

The AWD LOCK is not necessary. If the MO is sitting on snow and you apply the gas, the AWD system will engage as soon as wheel slippage is detected. The AWD LOCK does not need to be engaged.

-njjoe
 

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Running around with the AWD locked on should NOT void the warrantee. That would be really stupid. They gave you the feature to use. They have the cutoff at 6mph (on 2005+) to protect against damage.

Just because it doesn't affect the warrantee, though, does not mean it's not going to do damage. I would hesitate to use it unless you needed it (after all, that's the way it's designed). You could be doing damage that you don't notice until after the warrantee expires.
 

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The Murano is very different from typical 4WD vehicles.

The Murano is a normally Front Wheel Drive (FWD) vehicle. When the AWD kicks in it also provides power to the rear axle. But, both the front and rear differentials are open. Neither front nor rear differential has a limited slip or locker capability.

Undo stress points while turning on typical 4WD vehicles are the front CV joints that are not designed for all time use IE frequent and sharp turning. The half shafts on a FWD vehicle do not have this problem as bad because they are designed for constant use including tight turning. Now for 4WD vehicles that have limited slip or locker differentials on the front axle that stress can be exacerbated. With a locker differential, it has a ratchet mechanism that ratchets in turns but requires a lot of force for it to ratchet. Limited slips depend upon the strength of the friction plates or viscous coupler some are mild (OEMs usually are) some are tough. Straight line driving stress on typical 4WD vehicles is the 4WD transfer case itself. THere is a build up of stress between the front and rear axles because the effective gear ratio between the two is not a perfect 1.0. Essentially the load builds up in a twisting moment until something lets go, hopefully just a tire will slip a little. The belt or chain type transfer cases in typical 4WD vehicles can be used all the time in slippery conditions but not on dry pavement. The failure mode of these if used on dry pavement was the chain belt. Full time 4WD vehicles used to have gear to gear transfer cases which tended to eat u joints. Nowadays they use a viscous slip coupler in the drivetrain that will ease off the moment buildup and it is typically the failure mode. The Murano has none of these.

What happens with the Murano is an electrical solenoid actuates the AWD rear axle coupler that connects the output of the front transfer differential to the rear axle differential. Think of it as essentially an electrically actuated coupler in the middle of the drive shaft. That AWD coupler is not designed for full time use. It isn't strong enough and I'd bet it has a heat buildup problem too. Turning will put extra stress on this coupler as the effective ratio between the front axle and rear axle changes. I do not know what duty cycle the AWD coupler is designed for but I'd bet it ain't much.

As I've said before, the Murano is not an off roader. It is marketed as an urban SUV. There are many many reasons for this, one of which is the AWD system. It is designed for the occasional slippery spot that requires AWD. If you want a serious 4WD vehicle get yourself an old truck (one you don't mind getting scratched and dented) put a Detroit locker on the front axle and Brute limited slip on the rear. Then you can get stuck on a mountain slope, leave it in gear, get out, walk around the truck, and watch all four wheels spinning digging 4 really neat holes as you realize you should have put the winch on the REAR bumper.
 

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Enforcer said:
If you want a serious 4WD vehicle get yourself an old truck (one you don't mind getting scratched and dented) put a Detroit locker on the front axle and Brute limited slip on the rear. Then you can get stuck on a mountain slope, leave it in gear, get out, walk around the truck, and watch all four wheels spinning digging 4 really neat holes as you realize you should have put the winch on the REAR bumper.
:D Sound's like the voice of experience. Yes?

-njjoe
 
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