# Misconceptions about 4x4 and AWD



## fingersandclaws (Oct 17, 2005)

Was doin' a little research to see if my ML320 would be an okay beach vehicle and found this:

http://www.allpar.com/eek/k/SUVs.html

I don't know about accuracy, but a couple sites back up what this guy says.


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## Ryan Y (Dec 1, 2005)

*ive read that before...*

It can give you a better understanding of four wheeling. The last CJ-7 I built and the first wrangler I bought, I added lockers to the rear wheels to lock them up when wheeling.
My dakota is all wheel drive, then I have to switch it to four wheel on the beach.

A good trick to do is to be in a parking lot, put your rig in four wheel drive, turn the wheels all the way over left or right and try to drive. If its binding and doesnt want to go, youv'e most likely got the four wheel type like the first paragraph explained.

Thats another way to also check and see if the four wheel drive is working in a used vehicle that you want to buy....


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## FISHIN ROD (Feb 12, 2003)

*jeep 4x4?*

I have a 2000 grand cherokee limited and it has quadradrive. it says 4x4 and has seemed fine on the beach. since it is full time 4 wheel drive is that just another name for awd? Its a great little ride but I always wonder about that quadradrive stuff.


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## ReelinRod (May 29, 2003)

FISHIN ROD said:


> I have a 2000 grand cherokee limited and it has quadradrive. it says 4x4 and has seemed fine on the beach. since it is full time 4 wheel drive is that just another name for awd? Its a great little ride but I always wonder about that quadradrive stuff.


Jeep has undergone an evolution in its drive systems. Quadratrack, Quadratrack II and now Qudradrive . . . Basically they do the same thing, act as a differential in the transfer case to take up the ratio change from front to back when turning. They do this with a fluid that changes thickness when heated; wheel spin causes heat, heat causes the fluid to change viscosity and thicken and transfer power between two plates to front and back axles equally.

The vast majority of trucks do not have any differential in the transfer case, when it is engaged the front and rear are locked together. That's why what Ryan is describing happens when turning on pavement; it is called _transfer case windup_, it is very bad and can break stuff (gears, u-joints, hubs, even axles).

Whenever a non-Jeep driver has 4X4 engaged they should only be driving on a surface that permits a degree of tire spin (to relieve the transfer case binding).

Found on the web:

QuadraTrac ( ZG ) uses a viscous centre coupling biased virtually 100% rear wheel drive. The front and rear prop shafts are each attached to a set of rotors which are inter-spaced within a housing filled with silicone fluid. When the vehicle is travelling normally, the rear prop shaft is receiving drive. Because in a Jeep, we have fixed front hubs, the whole front drive train is rotating as we're driving down the road. Therefore, the front shaft and rotors are also turning at exactly the same speed as the rear rotors within the viscous coupling.
When we have a condition that causes the rear wheels to turn faster than the front ( eg. dirt or wet road, heavy right foot ) this causes a speed differential within the viscous coupling - the rotors attached to the rear shaft are now turning faster than the ones attached to the front. This causes the silicon fluid to churn between the interspaced rotors, causing heat. The viscous fluid goes very thick quite quickly and effectively provides up to 100% of the available drive to the front. Consider it an automatic centre locker. Toyota and LandRover use a similar device but normally biased 50/50 front/rear. The Jeep rear wheel bias preserves a degree of rear wheel steering which improves handling dramatically compared to a fixed 50/50 bias.

With the WJ, Jeep went to QuadraTrac II. Basically the same principle, but using the new gerotor pump device. Similar idea, but instead of depending upon silicon fluid heating up and going hard to provide drive, the speed differential within the chamber pumps transfer case fluid from one small chamber into another which engages a clutch pack. This system can withstand higher, fluctuating torque loads and does not need to heat up or cool down to be effective. The other benefit is if the pump fails, we don't have silicon fluid running throughout the transfer case stuffing everything up.
QuadraDrive went a step further and equipped the front and rear axles with gerotor pumps. Effectively the system is constantly trying to provide equal torque to each wheel. The system is brilliant because it's hydraulic-mechanical, tunable ( with different viscosity fluids ) and requires no driver input or electronics. You could argue that lockers are better because there's no need to wait a second for the wheel-speed differential ( wheel spin, dust, flying stones etc, ) but lockers don't have a limited-slip quality and they need the driver to control them. Different systems demand different driving techniques.
Now, the confusion begins. With WK/H, Jeep has re-designed all their transfer cases. QuadraTrac I is now an All Wheel Drive system ( no low range ), QuadraTrac II has an electronic-mechanical centre diff with brake-based electronic traction control and QuadraDrive II uses three electronic-mechanical diffs.
Whew!
Why change to electronic systems?
1. Possibly cheaper.
2. Infinite tunability. Instead of going for a crazy, overcomplicated gimmick like the new LandRover Terrain Response, Jeep can programme the computer using 'fuzzy logic' to do everything for you except select low/high range.
From what I've read so far, QDII has all the reliability and torque management benefits of QDI but will react much faster and can even predict traction loss before it happens.
No doubt Jeep still leads the way in drive systems - we've got the best high-tech system and the best tradtional system ( RockTrac+lockers+hybrid LSD on Rubicon ) available.​


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## BLUESMAN (Nov 4, 2003)

*4WD issues*

I think the first thing that everyone forgets is that unless you have limited slip or locking axles 4WD is really 2WD. One wheel on each axle will always free-wheel to compensate for turns (differential).

I have a 95 Cherokee with partime 4WD and the factory limited slip in the rear axle. This jeep is really great on the beach, both rear wheels drive with limited slippage and when I put in 4WD at lest one of the front wheels drives.

I bought a new Rubicon it has part time 4WD with air activated lockers front and rear. That means with the lockers activated both front wheels and both rear wheels are locked to each other and driving - real 4 wheel drive. To be truthful with you it's overkill, the Cherokee with the limited slip was more than adequate - I could tow with the Rubicon.

All these drive and traction issue go away if you *air down*, have ground clearance, and drive sensibly.


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## fingersandclaws (Oct 17, 2005)

Thanks everyone for your input. I'll let you guys know how I did after the first trip.


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## Woodchuck (Jan 5, 2005)

*Guess I’m old school on this one.*

All, except one, of the 4WD vehicles I have owned (4 jeeps and 3 trucks) were what I know as a 4x4. You drop it in gear, let off the clutch and all 4 wheels are driving. I have not owned, or driven, one of the fancy ones with lockers in them. I had a 1978 F150 where only one wheel front and one wheel back would spin. Limited slip or some such garbage they called it, useless. After the third time of getting stuck in its own shadow it was traded for the Chevy.

The way I look at it is if I am going to put it in 4WD, I am gona use it. It ain’t gona be a dry paved road and I ain’t gona be going like a bat outta Hades. If it is a paved road it is snow covered or icy. Yes, it will grunt a little and give ya some bucking if it is dry or hard dirt and you are turning tightly. To fix that… the gas pedal is the one on the right. Give it a little gas, the inside tires will turn faster and it will still get you where you want to go. I did say a LITTLE gas, not stomp it to the floor, just enough to break traction with the stubborn wheels. Just the way I have always known it.


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## lipyanker (May 31, 2006)

*expeditions no joke*

I dont know his opinion of the expedition seems a little one -sided so I began checking out some 4wd enthusist oriented sites and his opinion is just that and I cant wait to get my new one in sept.
It was you guys who encourged me to go out and give the sand a try and now I am hooked. aIl i need something reliable and that seems to be my expo. But that f650 does turn my head

http://www.f650pickups.com/page0009.html


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## Guest (Feb 21, 2007)

Has anyone that own a vehicle with limited slip-differential have any issues on the sand?


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## BLUESMAN (Nov 4, 2003)

*Only positive issues!*

With my Cherokee I only pull in 4WD when it wallowing - usually the down side of the ramps where its deep and soft. *Always Air Down!*


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## Reeltime (May 12, 2007)

*95 Pathfinder*

havent took snow white on the sand yet but i feel she will do okay has 4wheel drive whenever i have got in the mud she gets me out just fine. Anybody have a nissan and know what they air down too?? Would love to know oh yeah a ? bout what ever one else was talking bout. My other truck Ford Explores has all wheel drive wanna know if i take the ford will i have to have someone get me unstuck??


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## Tinybaum (Mar 8, 2004)

Reeltime said:


> if i take the ford will i have to have someone get me unstuck??


It's a ford, of course you will. :beer: :beer: :beer: 

18 - 20psi is about where you want to lower it. 

Tiny


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## F I LetsGoFishin (Apr 24, 2007)

*What about older 4x4*

In all this where do the older type 4x4's fit? 
I drive an 83 Full size cherokee that i always understood as true four wheel with part time transfer and manual hub locks. It is stated not to drive on hard surface when shifted into 4 high or low and has limited slip in the rear only. 
I do noticed that when it is high-centered all but 1 rear tire will spin.


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## Huntsman (Mar 6, 2003)

*Ha Ha Ha - Stv...*



Tinybaum said:


> It's a ford, of course you will. :beer: :beer: :beer:
> 
> 18 - 20psi is about where you want to lower it.
> 
> Tiny


I have a Merc Mtnr - and have had no problems w/ her on the beach. AI or OBX, even 3R's on one occasion but I got the heel out of there quick cuz I didn't have an ORV pass... LOL... 

Only issue I've had as Blues stated was at a high exit area - OBX - got a little spin but back her down and eased her back up. 

W/ the AWD just be sure to have your air down less than the norm.. I usually go to 15-18 and have done well. So, Yul you shouldn't have a problem. If you need a tow rope for that Cedez just give me a holla...  

BTW Steve - looking into that 1500 when I get to NC...


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## fingersandclaws (Oct 17, 2005)

Thanks B, but I think we're good 2 go. Besides, I've got a car full of grown men, their just as good as a tow strap


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## Huntsman (Mar 6, 2003)

fingersandclaws said:


> Thanks B, but I think we're good 2 go. Besides, I've got a car full of grown men, their just as good as a tow strap


Make sure Jiro and John aren't sitt'n on the same side.. wouldn't want you to be weighted unequally to either side... LOL.. .

See you fellas out there... Are you just fishing Saturday or Fri/Sat?


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## fingersandclaws (Oct 17, 2005)

Day-um . . . your one cold brutha  We'll hit the bridge Friday night/Sat early then head over to AI.


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## eternity059 (May 30, 2007)

Reeltime said:


> havent took snow white on the sand yet but i feel she will do okay has 4wheel drive whenever i have got in the mud she gets me out just fine. Anybody have a nissan and know what they air down too?? Would love to know oh yeah a ? bout what ever one else was talking bout. My other truck Ford Explores has all wheel drive wanna know if i take the ford will i have to have someone get me unstuck??



I took my Pathfinder out on OBX and aired down to 15psi like Huntsman said and I was fine. I put it in 4wd Hi and drove like a grandma and followed everyone's tracks.


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