True 4WD/AWD?

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actionstan

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Hello All,

My understanding (correct me if I am wrong) a typical differential, be it 4WD/AWD/FWD/RWD will always send power to the wheel/wheels with the least path of resistance. So if you are on ice/mud/snow and spinning, you will continue to spin even if you have a tire/tires that are on a stable surface.

I understand some differentials are made to prevent this slipping so you can get grip to all tires, but unaware if these come stock on any vehicles and wonder if there are downfalls for daily driving.

My question, Do any stock consumer vehicles actually have a system where they are "true 4wd/awd"? so that all 4 tires will spin regardless of what surface they are on? I am curious as I eventually want to get a vehicle I can depend on in most situations, and possibly pull someone else of a bad situation if needed, but it will also have to be a decent daily driver.

Thanks all!
 
This is a complicated question. Many vehicles can be ordered with limited slip or locking differentials in the rear. My favorite option here is the automatic locker available as an option on many full size trucks. My work Tahoe and F-150 are both equipped in this manner.

Modern traction control systems can also apply the brakes to the wheels that are slipping, although I've found that this is less effective than a mechanical locking differential.

There are just too many variations to explain them all, although there are plenty of articles where you can read about this. My Subaru for instance; the power is split 50/50 full time between the front and rear, and side to side is managed by traction control selective braking.

If you're looking for the best possible solution, get a truck with an automatic locker, four wheel drive, and a good set of all-terrain tires. I've found that the Goodyear Wrangler SilentArmors are the best for winter conditions.
 
What kind of vehicle type are you considering???

There are no general rules about AWD. Just different derivatives that offer at least more traction than 2 wheels when needed to extreme traction always or actively making the vehicle handle better.

Trucks with primitive 4wd are not always the best solution for in between conditions. Subaru offers relatively inexpensive AWD cars/CUVs with incredible ability to put power down to a wheel with traction in simple reliable systems. Subaru at its core is designed to be AWD unlike majority of FWD vehicles out there were its an engineering jury rig.
 
I think my Audi comes very close to what you are looking for, only if I turn of the ESP. I usually do this in winter weather, because if I don't it will cut the throttle and use selective braking to control wheel spin which when you pull out into traffic is not the best thing to have happen.

With the ESP off, it will spin all four tires as long as I keep my foot on the gas and keep it pointed straight. Even with the ESP off, if it get sideways enough, the yaw sensor will trigger the stability system to ignore the ESP being off and try to right the car.

The front and rear diffs are open though, so I guess there may be a time where it will not spin all 4 tires. I haven't had that happen to me yet.
 
Jeep in many vehicles has a transfer case setting with 2WD, 4PT and 4WD. The 4PT locks up most of the wheels and can only be used on snow covered roads where there will be some slipping on the snow of the wheels anyway. If driven in dry pavement one will hear lots of clunks and groans.
 
Originally Posted By: rjundi
What kind of vehicle type are you considering???

There are no general rules about AWD. Just different derivatives that offer at least more traction than 2 wheels when needed to extreme traction always or actively making the vehicle handle better.

Trucks with primitive 4wd are not always the best solution for in between conditions. Subaru offers relatively inexpensive AWD cars/CUVs with incredible ability to put power down to a wheel with traction in simple reliable systems. Subaru at its core is designed to be AWD unlike majority of FWD vehicles out there were its an engineering jury rig.


Not really picky, I want something that is good for a daily driver, that at least gets OK gas mileage.

I have so far, been looking at subaru legacy's, and Jeep Cherokees, and various trucks/suvs from all manufactures, ford/chevy/dodge(not quiet as much dodge), nor am I opposed to any Asian make, but they seem to cost a little more. I also need something that can accommodate a car/booster seat as I have a child, so any single cab truck is out of the question
grin.gif
 
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Originally Posted By: Bandito440
This is a complicated question. Many vehicles can be ordered with limited slip or locking differentials in the rear. My favorite option here is the automatic locker available as an option on many full size trucks. My work Tahoe and F-150 are both equipped in this manner.

Modern traction control systems can also apply the brakes to the wheels that are slipping, although I've found that this is less effective than a mechanical locking differential.

There are just too many variations to explain them all, although there are plenty of articles where you can read about this. My Subaru for instance; the power is split 50/50 full time between the front and rear, and side to side is managed by traction control selective braking.

If you're looking for the best possible solution, get a truck with an automatic locker, four wheel drive, and a good set of all-terrain tires. I've found that the Goodyear Wrangler SilentArmors are the best for winter conditions.



I would say I agree with everybody in this thread except for you. Not saying you're wrong, but I don't agree. A 4x4 truck with a traditional locking diff will get stuck in the mud very quickly, with equal tires, compared to something with a computerized AWD system like a Subaru, or something thats purpose-built for off roading like a Jeep. Modern traction controls are absoltuely fantastic for non-ideal driving conditions. I teach car control & defensive driving, and it's amazing what you can do and see when you can switch back and forth between TC on or off.


But you are correct, it is a complicated question, and there are many different types of 4x4/AWD that have different design goals, and overall are 'better' at one task vs another, be it high-speed stability in poor weather roads, getting out of the mud, rock crawling, trying to move a very heavy load, etc.
 
Originally Posted By: actionstan
Originally Posted By: rjundi
What kind of vehicle type are you considering???

There are no general rules about AWD. Just different derivatives that offer at least more traction than 2 wheels when needed to extreme traction always or actively making the vehicle handle better.

Trucks with primitive 4wd are not always the best solution for in between conditions. Subaru offers relatively inexpensive AWD cars/CUVs with incredible ability to put power down to a wheel with traction in simple reliable systems. Subaru at its core is designed to be AWD unlike majority of FWD vehicles out there were its an engineering jury rig.


Not really picky, I want something that is good for a daily driver, that at least gets OK gas mileage.

I have so far, been looking at subaru legacies, and Jeep Cherokees, and various trucks from all manufactures, ford/chevy/dodge. I also need something that can accommodate a car/booster seat as I have a child, so any single cab truck is out of the question
grin.gif




Subaru is then your best option. VERY safe cars, and great AWD system that will get you around in ANY weather. High center ground clearance, very reliable, and get mid-high 20's mpg (unless you look at an Imprezza, they get low 30's).
 
IMO if you are wanting "on road" traction, probably almost anything with AWD and traction control will be close enough to giving you max pull from all four tires.
Even without TC you can drag the brakes on an open diff vehicle to make it pull with all 4 tires.
I've pulled a few cars around with my 3000lb open diff Tracker and its done fine with snow tires on. A 6000lb pickup will pull twice as much of course, but I need mileage, not a tow truck.
 
Originally Posted By: skyactiv
Get a Subaru. http://www.youtube.com/watch?v=FOmZIu_y1js

http://www.youtube.com/watch?v=-AlU480nHHw

http://www.youtube.com/watch?v=c2gy_6Jbu9g


Wow that's exactly what I am looking for, unless these are just some Subaru propaganda videos lol. At least one of the videos made the claim it was a independent study.


Do all subarus have this technology new and old? or was there a certain year this was put into place? That really has me torn because I had almost settled on a older jeep cherokee for various reasons.
 
Find videos on youtube of jeeps with everything locked ("spools" for differentials) and them doing various offroad stunts.

This would be insane or at least very tiring in an on-road vehicle.

I agree with the subaru reccomendation. Realistically any borderline weather that would have you stuck in, say, a cherokee and free in a subaru (or vice versa) would have traffic jams, plows unable to get through, the National Guard out with bulldozers, etc.
 
Some Subarus have viscous-coupled limited slip rear diffs. The systems are also designed to provide traction in slip situations. The 5-sp manuals with a viscous coupled transfer case will lock up to some degree. Other systems from Subaru use electronic management to transfer power (front or rear) to the wheels with the most traction.
 
+1 on Subaru, here is some real world non-propaganda:

http://www.youtube.com/watch?v=93L9JMbQI3E

Please ignore the Russian singing however.........

The simulated limited slip via individual wheel braking is part of the Vehicle Dynamics Control or VDC which became std equipment I think in model yr 2008. Subaru's strong point is snow, they can do off-road as obvious in the video but they are not technically meant for serious off-roading.

Originally Posted By: actionstan


Wow that's exactly what I am looking for, unless these are just some Subaru propaganda videos lol. At least one of the videos made the claim it was a independent study.


Do all subarus have this technology new and old? or was there a certain year this was put into place? That really has me torn because I had almost settled on a older jeep cherokee for various reasons.
 
Originally Posted By: actionstan
so that all 4 tires will spin regardless of what surface they are on?


Any vehicle capable of spinning all four wheels at the same speed would have to have front and rear differential lockers. The only stock consumer vehicle on the market I am aware of coming with both front and rear E-lockers is the Jeep Rubicon, I believe it can come stock with Dana 44 axles. Subaru may have a highly advanced AWD system no doubt but it will not outperform a vehicle equipped with front and rear %100 positive differential locks, nor will a Subaru outperform a vehicle with a larger ground clearance like a jeep. If you want to be prepared for a worst case scenario winter storm practice airing down your tires to 12-15PSI, it's an ages old traction aid that works.
 
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Whoever wrote that wiki forgot to include Forester in the lineup. However, since the Forester shares the same platform as Impreza, it could simply be shown as Impreza/Forester in that wiki. Overall it seems accurate enough. The automatic transmission models, Impreza/Forester at least, from model yr 2008 forward run in a default torque split of 60/40 f/r most of the time and can change to 50/50 as needed, a Multi-Plate Transfer (MPT) clutch is used in the auto trans. The whole torque split thing and Subaru AWD "how does it work" etc has been beaten to death over on SubaruForester.org.

If you live where you're off-road a lot or you have to get to serious off-road places a lot then something like a Jeep would be better. But if, like most folks, you find yourself on streets most of the time and gravel/dirt roads, fire roads, and trails when you're "out in nature" then it's hard to beat the comfort and efficiency of the Subaru Forester or Outback. The 2014 Foresters with the CVT are easily tagging 30+ mpg highway and mid to high 20's in mixed city/suburban.

Oh yeah. 2014 Subaru Forester was Motor Trend's SUV of the year, article is online. I suppose it won for being a well balanced "jack of all trades."

Originally Posted By: simple_gifts
A BITOG'r (97prizm) pointed out to me that all Subaru AWD systems are not created equal; a fact they seem to leave out.

I was pointed to this link

http://www.awdwiki.com/images/SubaruSymmetricalAWD2.doc

to get the differences explained; perhaps a Subaruphile can confirm/rebuke.
 
I appreciate my Subaru in most weather, but when it comes to the worst of the winter stuff, my 2012 Tahoe work truck equipped with an automatic locker, proper all-terrains, and the 4WD selector on Auto outperforms the Subaru by a wide margin. The Stabilitrak has saved my butt on more than one occasion too.

If the OP wants to be able to tow someone out of a ditch, that's the way to go. If it's a commuter vehicle and you have the option of waiting for the plows to clear the roads, the Subaru is a better choice.
 
Originally Posted By: actionstan
Hello All,

My understanding (correct me if I am wrong) a typical differential, be it 4WD/AWD/FWD/RWD will always send power to the wheel/wheels with the least path of resistance. So if you are on ice/mud/snow and spinning, you will continue to spin even if you have a tire/tires that are on a stable surface.

I understand some differentials are made to prevent this slipping so you can get grip to all tires, but unaware if these come stock on any vehicles and wonder if there are downfalls for daily driving.

My question, Do any stock consumer vehicles actually have a system where they are "true 4wd/awd"? so that all 4 tires will spin regardless of what surface they are on? I am curious as I eventually want to get a vehicle I can depend on in most situations, and possibly pull someone else of a bad situation if needed, but it will also have to be a decent daily driver.

Thanks all!



Toyota's CRAWL Control system takes a different approach than has been discussed here so far.

With CRAWL Control, the vehicle's control systems apply power and braking to all four wheels independently. If a wheel is slipping, braking will be applied to just that wheel. If a wheel has grip, power will be applied to just that wheel. If all four wheels are gripping, power will be applied to all four wheels.

Search around the internet for "CRAWL Control" and you will find many videos showing how this system can get you out of a lot of trouble - better than locking differentials.

Here's one video that has a simple overview: Toyota CRAWL Control System

thumbsup2.gif
 
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