[trevmiesterj]

So our little valley in Idaho received a stunning 14 inches of heavy heavy powder yesterday. The snow was so thick and so dense that vehicles were getting stuck everywhere. And it didn't matter what people were driving-4wd trucks, SUV's, and especially cars were defenseless against the huge ruts and powder burms. The city wasn't able to keep the side streets plowed, so it was martial law if you were unlucky enough to get stuck.

My wife did get stuck outside of our driveway in the MO when it high centered on a large drift, and was able to make it out with some assistance from some neighbors. She wouldn't have been even driving in the slop but wanted to meet some friends that were in for the holidays.

Anyway, I met with her after coming back from skiing, and it was up to me to navigate the MO through the now even more heavily covered roads. I put the rig in AWD lock and powered through, making it home through the carnage before blasting into my unplowed driveway and getting stuck about half way up (hooray-I was off the street!)

My question is this:

If the AWD system only kicks in when it feels slippage, then what about when every inch of street is slippery? Does the system, even with the lock on and over 20 miles per hour, sustain AWD or just detect when it needs it?

Anyway, brilliant sunny day here today and the streets are clear. I just have a lot of shoveling to do...

 

[Doombringer]

I'm curious about this too.

I'm not sure an entire road can be slippery. It might be slippery in theory (it has ice on it) but to a vehicle it is different. It tries to detect slip and then engage traction control/AWD, so I think it only comes in bursts.. nothing sustained above 20 mph.

Could be wrong, though

 

[dmako]

I think it works as follows:

Mostly a FWD vehicle. When traction is lost, some (up to 50%) of the power will be diverted to the rear tires. With normal AWD, slippage does occur which allows easy turning but leaves you with essentially 2-wheel drive i.e. one front wheel one rear wheel.

However if the AWD lock is on, all four wheels have equal power applied to them hence hard to turn at speed.

If I understand it correctly, you can lock all four wheels up to 18 or 20 MPH, then the system will revert to normal AWD. Once you go below 18 – 20MPH it will re-engage true 4-wheel drive.

 

[dmako]

Murano All-Wheel Drive

The Murano's AWD operates in front-wheel drive until wheel slip is detected. It will then send the appropriate amount of power to the rear axle as needed. No driver input is required. The AWD system in "Auto-mode" operates from a 100% front-wheel drive condition to a 50% front 50% rear power split, or any variation in-between based on vehicle needs and road conditions. A transfer gearbox near the front differential turns a driveshaft to the rear axle. This driveshaft is always turning when the vehicle is moving even though power may not be needed at the rear axle. An electronically-controlled multi-plate clutch pack is mounted in the rear differential housing to direct power to the rear axle.

An "AWD-LOCK" switch will give a fixed 50/50 power distribution front to rear at speeds of approximately 19 miles per hour (30kph) and below. When speeds rise above 19 mph, the AWD Controller will determine power distribution front to rear based on vehicle needs and road conditions. When speeds drop to 19 mph and below the fixed 50/50 condition will resume. According to Nissan, AWD LOCK is intended for low-speed, low traction conditions only.



The AWD Drive Coupling contains two clutches: The control clutch is triggered by an electric magnet that receive signals from the AWD Controller. The control clutch operates a ball bearing cam mechanism that determines the amount of pressure to the main clutch assembly. The main clutch assembly transfers power to the rear axle according to the pressure of the control clutch. Full pressure (clutches locked) gives a 50/50 power split. Less pressure varies the power transfer to the rear axle.

 

[trevmiesterj]

DMAKO,

Thanks for the terrific reply. I have noticed, at least it seems so, that the AWD LOCK seems to have more torque when engaged at low speed, this may be because of gearing initiated by the transfer mechanism.

INYO, Is it appropriate when the roads are snow covered to leave the vehicle in AWD LOCK for an extended period of time?

 

[dmako]

I plan on using the lock only when going up my icy driveway. Other than that normal AWD should be fine.