| darrylburke |
Well... I finally got a chance to put the MO to the ultimate test last night..
I was parking on a side street in toront,where some of the plows had missed.. and the snow was about 5 to 10 inches high (soft anad hard sections)...
I managed to get it in easily, but I guess the car settled while I was out.. when I tried to get out.. one side (the curb side) was sitting higher then the street side..
NO PROBLEM.. (I thought...) put it in AWD lock, and started to slowly try the gas.. "SPIN".... "SPIN".. "SPIN" the front right, and rear right were going round and round.. both left sides,, NOTHING..
so much for those marketing claims of "transfering power from the wheels that slip to the wheels that grip"... |
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| Tyler_Canada |
Do a forum search for "differential" and read some of the threads.
Here is a quote that is applicable:
quote:
Also, the differentials in the MO are "open".
An AWD or 4WD that has "open" differentials means that it is really 2WD, 1WD on the front axle and 1WD on the rear axle. A FWD only or RWD only vehicle with "open" differentials really has only 1WD.
On these vehicles, you can gently press on the brakes and it will act like a limited slip differential splitting power across the axle to both wheels. But it's hard on brakes, only used when you get stuck.
A "true" 4WD will have limited slip or detroit locker differentials. I built a Ford F150 for offroading and put a detroit locker on the front axle and a limited slip on the rear axle with manual front hub locks. I still got stuck, left the truck in gear, got out and walked around the truck watching all four wheels spinning. That's why they make winches.
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| senza |
| To take full advantage of the AWD system with "open differentials" you should reduce the ability of each wheel to spin...on snow and ice this means a set of winter tires...18" sizes are few and far between plus expensive...hopefully this will improve next winter..the considerable expense of a 2nd set of wheels/tires can be justified if you plan on keeping your vehicle 3 or 4 years.. |
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| Snowride |
| I'll second that as I was able to do a direct comparison since i was in a snow storm when on my way to have my winters installed. I was questioning why I was doing this because the vehicle worked so well with the 4 seasons radials on the way there. Unbelievable difference with the Dunlop Grand Trek tires on. They are just as quiet and comfortable as the stockers but what a difference in traction and braking. You really have to try it to believe it. |
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| Eric L. |
| Yes unfortunately the one wheel per axle slipping situation will immobilize a Murano (or any other AWD crossover for that matter). Just out of curiousity, do you have VDC? VDC includes traction control and will cut power to wheels that slip on the front axle. |
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| senza |
| I don't have VDC but there is some form of traction control...when "booting" it from a stop in slippery conditions if you allow excessive wheel spin, engine power is cut for 1 - 1 1/2 sec. and then power returns... |
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| Eric L. |
| Hmmm I thought the limited slip front differential was the traction control, but only on VDC vehicles. Perhaps the jump from FWD to AWD is the delay you are feeling, although I have never felt the transition myself. |
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| Tyler_Canada |
On the Murano, if front wheel slippage is detected, an electronic clutch in the rear differential is engaged, sending between 0% and 50% power to the rear wheels. If AWD lock is enabled and the vehicle speed is below 19MPH, there is 50% power going to the front and rear pairs of wheels.
Both front and rear differentials are open. This means that if only one wheel in a pair (front or back) has traction, the power will go to the wheel without traction. If you have both wheels on one side of the vehicle without traction (on ice, mud, etc.), you are in trouble.
TCS
If you step on the throttle enough that the front wheels slipped AND when the rear wheels engaged they slipped too THEN
the Traction Control System engages, reducing throttle output.
VDC
If you slide sideways somewhat, the Vehicle Dynamic Control engages, causing the ABS to brake the wheels on the inside of the slide. This sends power to the wheels outside the slide. You would feel the shudder associated with the ABS if this is the case.
If you hit the VDC Off button, you disable both TCS and VDC. |
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| senza |
| The front / rear wheel spin followed by reduction in power feels like a TCS being activated, yet my vehicle does not have VDC. Perhaps TCS is part of AWD and separate from the VDC system? |
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| Eric L. |
quote:
Originally posted by senza
The front / rear wheel spin followed by reduction in power feels like a TCS being activated, yet my vehicle does not have VDC. Perhaps TCS is part of AWD and separate from the VDC system?
If you do have traction control, the SLIP light will flash on your dashboard when TC is active. |
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| CVeeT |
I am positive, TCS is part of VDC. If you don't have VDC package, you DO not have TCS.
In that case only auto-engaging all wheel drive and ABS comes to your rescue.
Strange, I have VDC, I have taken my MO to spin or slide in snow and slush, I can feel the vibrations of ABS but never have noticed TCS light flicker. May be I did not make it bad enough for it, I am just impressed with the bad weather performance of MO. Has handled flawlessly and with sure footedness. |
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| Tyler_Canada |
| It's the SLIP light. It blinks a couple of times, then shuts off. It's hard to notice, especially if you have your steering wheel tipped up a bit like I do. |
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| darrylburke |
Eric:
the funny thing was.. not once did the "slip" light come on.. it does come on when I'm driving and slide the back end out.. but not when I was stuck..
also I noticed.. I tried to "rock" the car back and forth.. the time it takes the transmission to switch from reverse to drive is about 1.5 seconds (even though the shifter was changed quick..) there seemed to be a big delay (enough so that rocking was impossible)
quote:
Originally posted by Eric L.
Yes unfortunately the one wheel per axle slipping situation will immobilize a Murano (or any other AWD crossover for that matter). Just out of curiousity, do you have VDC? VDC includes traction control and will cut power to wheels that slip on the front axle.
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| senza |
| Slip light doesn't come / no VDC so I guess the power reduction is not TCS...I wonder if it is some form of safety feature of the CVT..if it senses excessive wheel slippage at low speed it shuts down power to prevent a shock once traction is attained??? I'm grasping at straws here fellas.... |
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| Eric L. |
quote:
Originally posted by senza
Slip light doesn't come / no VDC so I guess the power reduction is not TCS...I wonder if it is some form of safety feature of the CVT..if it senses excessive wheel slippage at low speed it shuts down power to prevent a shock once traction is attained??? I'm grasping at straws here fellas....
Your idea sounds correct to me. Or maybe there is no loss of power, and you are just feeling an odd way the Murano's 4 tires grab for traction. It could be an artifact of the mediocre Goodyears. |
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| senza |
| Don't think its related to the tires...I replaced the Goodyears at 1000 kms with Yokahama Geolander Go52's 265x60x18..very pleased with their performance and looks...not being an engineer or a "techie", after reading up on CVTs I think the excessive wheelspin under low engine load caused by very poor traction situation causes the CVT controller to read an abnormal "situation" and sends a command to the ECU to reduce power...it's not a problem and is probably a good thing..I just like to understand whats going on ... |
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| ekaxel |
| Does TCS do ANYTHING else but reduce power? No automatic brakeing on the slipping wheels? |
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| Tyler_Canada |
| No, it doesn't do anything else. |
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| dmako |
It's just how AWD works. My Jeep Grand Cherokee had AWD. I took that thing through some extreme off roading but would get stuck in my driveway on ice. i.e. 2 wheels spinning.
The MO needs some good air lockers :D |
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| senza |
| Most Jeep owners would be "offended" if you refer to their 4 wheel drive systems as AWD. Jeeps are solid(live) axel drive trains based on rear wheel drive with controlled engagement of front differential plus they have transfer cases / higher ground clearance etc.....the perception here is a rugged offroad go anywhere image....the Murano AWD system is great for 95% of most drivers needs...just can't handle mud bogs and 45 degree inclines... |
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| Tyler_Canada |
| Some Jeep Grand Cherokees are AWD. Most other Jeeps are 4WD. |
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| senza |
| "4 wheel Drive" and AWD are somewhat interchangeable...a vehicle that is rear wheel drive that you can shift into 4 wheel drive and that has a tranfer case, I would label "4 wheel drive" ; a car based vehicle that has the ability to transfer power to the rear wheels and no transfer case I would call "all wheel drive". Your right that newer Jeep GCs have a system that will transfer power to front wheels automatically if slippage occurs (AWD like). I think Jeeps latest system which has Mercedes parts can direct power to one wheel that has traction if the other 3 spin. |
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| dmako |
Yes my Grand cherokee (95) had AWD, my CJ has 4-wheel drive.
Much different systems. With 4-wheel drive all wheels turn at the same speed all at once. |
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| senza |
| I guess having a Murano and a "real" Jeep you get the total spectrum of AWD/4WD motoring pleasure....are the "lockers" after market or factory? |
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| GMTURBO43 |
I can't think of a stock vehicle that came with air lockers - the original Hummer maybe?
A standard locker is NO good for everyday driving. It really has no benefit outside of the occasional snowstorm that the average driver will encounter. Plus, I highly doubt there is one made for our application.
An air locker gives you the option to 'lock' the differential when needed. This will give you the best of both worlds. The smooth operation of an open diff and the ability to lock it when needed. |
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| senza |
| Some high end full size imports, Toyota Land Crusier comes to mind, had air lockers as an option, I think. |
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