Geico266

To all you 4 wheeling newbies out there, just remember one thing while you are passing all those gasser sliding around on the road;

1. 4WD don't help STOPPING at all, not even alittle!
2. The tow charge when you do get stuck (and you will) is 4 times that of a regualr car!
3. If you play, you pay.

I know its fun and all, but if you are new to 4WD just be careful out there!

NJMurvin

We don't get the white stuff around here. But, on a recent fishing trip in the Eastern Sierras, I found myself in a predicament. We were taking a look at a buddy's cabin that required going down a fairly steep gravel driveway. I was doing fine until I had to turn around. I pulled forward, then started to back up. The back tires started to spin and dig in. I tried for a few seconds to rock it and then remembered the little dial on the dash. I popped it into neutral, went into 4hi, and backed out of there like I was on dry pavement. I won't use the 4x4 often, but when I do, I'll be thankful for it.

I really bought 4x4 because I like the higher ride height (and my daughter nagged me to death to get it). Because of that experience and the ease in which I can move around my 5er in 4LO, I believe it was worth it.

Neil

t-15 firefighter

i'm with you. i can't seem to take a $45000 truck off in the woods but it was times like these that i am very happy that i have a 4X4. i also like the looks better than a 2 wheel drive.
but thats just my opinion.


britt

Fat Framer

OH yes it does, stomp on the brakes and throw it into reverse then mash the throttle. Now you have 4 wheels spinning backwards!

John Halter

Every 4x4 I have ever had stoped better in 4x4 than 2 wheel drive try it you will be surprised and it is a more controlable stop on ice.But I do agree when you get it stuck, and you will, it is usally stuck twice as bad and takes more money to get it out. Geting over confinent in a 4x4 will get you in trouble.

PapaPerk

Wetspirit....

I don't agree with your equal torque statement concerning open diffs. You can have one front wheel on ice and the other on pavement. The wheel that is on the ice will spin freely while the other wheel is stationary. If there was any "torque" being applied to the wheel with traction, the vehicle would move to do the friction of the surface to wheel contact patch. The differential is a intresting device. If both wheels have equal traction then both wheels receive equal torque from the engine and drivetrain. However if one wheel has no traction then all torque and rotational motion is transferred to this wheel. The transfer of torque is caused by the spider gears in the diff. In normal operation the spider gears do not rotate but rather orbit inside the carrier. However when one tire is held stationary (dry pavement) and one tire is free to rotate (ice) the spider gears now rotate and orbit inside the carrier. This causes an increase in tire speed (2x I think) and transfers all rotational movement to tire with no grip. The differential is a plantery gear train not unlike those found in an automatic trans. When limited slips are used the limited slip device controls the amount of movement the spider gears can rotate. If I am not mistaken our dodge trucks use a Torsen type limited slip. This setup is very unique in that is uses helical gears and has no clutches. This style of limited slip diffs is the most advanced I am aware of. Torsen diffs are used in some of the most advanced vehicles in the world like Audi, Porshce, etc. Plus I think F1 uses them in their race cars.

Just my 2 cents....

Tom Bolitho

Some of us are missing an important point. If you have a 4x4 with a locking rear end you have more that 3 wheel drive. When the t/case is in 4x the driveshafts are locked together. If one wheel in front is going to spin then at least one wheel in the rear must spin. If the rear diff is locked up then both front must turn at the same speed. It is possible to loose traction if both rear wheels are spinning, it will allow the front to spin one tire. A controlable locked in the front, either air or electric is definitely a plus.

1st gen Hobie

When you downshift in 4x4 you have two more tires slowing you down.

ed paul

lol,,remember my first glare ice experience with a 4X4,,the thing took off like it was on fly paper,,i was feeling real good about that,,,untill i had to stop! the only thing anti lock brake will do for u on glare ice,,is keep u sliding staight

Raspy

Papaperk and v8440,

Go back and take another look, and bear with me for a moment to understand what I mean.
Sometimes action on slippery surfaces can be misleading. Just because one wheel is spinning it doesn't mean it is getting all the "torque". Approach this with an open mind. Either wheel can spin but both are always getting equal torque in an open diff. That's the whole idea of a differential, ie. equal torque at varying wheel speeds compared to each other. Everything from a slight speed difference on a corner to one wheel stopped and one spinning wildly means equal torque. This allows us to go around corners with power to both wheels and without grinding the rear tires. The wheel spinning in the snow is putting a little torque to the ground, not much, but a little. And the one on the hard surface is putting exactly the same amount to the ground. To understand this you must see the difference between "torque" and rotational "speed".
Finding a diff with the cover off in a wrecking yard can be very enlightening.
The idea that one tire is getting all the torque is one of the old myths perpetuated by seeing a tire spin on slippery surfaces. Seeing one wheel spin does not mean it's the only one getting torque. It means it is the one limiting the overall torque being delivered through the system.
I love this subject because it just won't go away. Cracks me up.
Remember, I'm refering to "open" diffs here. Lockers offer modifications that overcome the open diffs problems.
As I posted earlier, the LS, or lockers, or any other type of traction enhancing differentials have some mechanism to attempt to make the wheels turn at the same rate. In other words, not letting one wheel rev up while the other one sits stationary. This has the effect of transferring more torque to the wheel that has more traction. In our case it's semi binding helical or worm type gears. If one wheel is stopped in a conventional open diff the other wheel turns twice as fast. In the AAM LS diffs if one wheel stops it can't use the conventional spider gears to double the speed of the other side. It's a wonderfully simple and effective arraingement. Pretty much invisible in normal driving. But not perfect for all out rock climbing.

PS. look up "differential gear" in a good dictionary.

Wetspirit

tdupuis

Power = Torque * angular velocity.

The torque may be equal, but the power isn't. Therefore, all the power goes to one wheel. Open differentials transfer power from the wheels that grip to the wheels that slip, on surfaces with poor traction that is. This then causes one wheel to spin ferociously, and the other one to just sit there. So yes, it is still 3-wheel drive when you need it most.

Give me limited slip differentials any day, thank you very much. Or just rear wheel drive... I'm pretty happy with plain ol' rear wheel drive.

Patriot_RAM

t-7 firefighter -- I think we got some of your snow up here in Fayetteville also. I was carefully trucking down the interstate when it hit passing all those poor souls in the ditches. The 10 mile stretch of 540 from Fayetteville to West Fork had about a dozen cars off the road. Three were on their tops including 2 Chevy 4x4's and a 4-runner. I stopped to make sure everybody was okay and kept on truckin'.

Oh -- The truck did awesome in Wisconsin early last week also.

PapaPerk

Wetspirit...

I have given your statements some thought and still do not agree. Lets reason all this out shall we?

First of all torque = force x distance. The distance is not distance of travel but distance between rotation axis and force applied to rotate object about the axis.

Now lets apply this first equation to our vehicle model. Our vehicle model is a rear wheel drive vehicle with a standard non-limited slip spider gear diff. One tire is on ice and the other tire is on dry pavement. With the vehicle stationary and power applied the tire on the ice will spin and the tire on the pavement will remain at rest. The only torque that is being applied to the ground by the tire at rest is the amount of torque that it is required to rotate the spider gears inside their carrier. And this torque is very minimal after the differential has reached a steady state operation. This is why a person is able to hold a vehicles tire stationary while the other tire spins (don't try this with limited slip!).

You made this statement in your last message. "Either wheel can spin but both are always getting equal torque in an open diff. " In my humble opinion this is completely false. In fact the differential does just the opposite. It transfers torque to the path of least resistance. Draw a free body diagram of the differential in the situation above and you will see what I am talking about...

Cheers...

fredbert

An open differential delivers constant torque to each wheel. The average speed of the wheels always equals the drive-shaft speed divided by the gear ratio. If you stop one wheel, the other will go twice as fast. v8440's "free-wheeling" test is entirely consistent with this. The small torque he resisted to keep one wheel from rotating came from friction in the rotating gears and bearings on the other side of the axle. The front differential of 4x4s is typically of the open type. This means when one front wheel of a 4x4 is spinning, you've got a 4x2!

A locked differential delivers constant speed to each wheel. The new Power Wagon has lockable differentials. They act as open differentials when not locked (except for the rear one if you opt for the below).

An anti-spin differential as Dodge calls it is really an open differential with a twist. It includes a mechanism which applies a load to the axle half that is spinning. This creates torque which is seen at the non-spinning wheel because it is still a constant torque device. That's what gets you moving, hopefully to the point where you have good traction at each wheel. I don't know why it's not standard on our favorite trucks, but be sure to get this option even on 4x4s and the Power Wagon!

I hope all this helps.

PS for tdupuis: I'm glad to see there's at least one other 4x2 fan in here!

t-15 firefighter

Wow!

you guys are hurtin my head.

all i really wanted to say was that my truck did great in the snow. open diff, 4X4, 4X3, whatever. i went anywhere i wanted without any problem. i couldn't be happier with my truck.


britt