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What does 4WD feel like
January 15, 2012 11:12 AM   Subscribe

What does four-wheel drive "feel" like? How would I know that it's on and operational?

Hi car folks. We have a 20-year old car with the option of four-wheel drive, activated by a button on the dashboard. Unfortunately, either the light that indicates that the four-wheel drive is in effect has burnt out or the four-wheel drive isn't activating. We would like to try to figure out on our own what the answer is before we take the car into the mechanic.

Why do we need the help? We just moved to Michigan and have never used four-wheel drive before, so we have no idea what it feels like if it's working properly. Would we be able to tell? What would working four-wheel drive feel like, and how would it feel like from normal driving? We had the car checked out six months ago by a mechanic before we left and he said that it appeared to be working normally then.
posted by foxy_hedgehog to Travel & Transportation (20 answers total) 2 users marked this as a favorite
 
Easy test, go somewhere that is either dirt or snow (parking lot) , have one person stand off to the side outside the car. The other person stomps on the gas while the outside person watches the front wheels. It will be easy to tell if the wheels are moving in a passive manner or are powered.
posted by HuronBob at 11:23 AM on January 15, 2012 [1 favorite]


Let me add, it will be almost impossible to tell if it is in 4x drive on dry, hard pavement, and you shouldn't be using 4x on dry pavement anyway, it can damage the drive train.
posted by HuronBob at 11:28 AM on January 15, 2012


Take the car to a shop where you can lift all four wheels off the ground. ;-)

Failing that ... cars with optional 4WD often lose a bit of turning radius.
posted by Cool Papa Bell at 11:29 AM on January 15, 2012


Another (admittedly hacky) way to tell is to get the car onto some mud, stomp on the gas and see which wheels are slipping.
posted by Cool Papa Bell at 11:31 AM on January 15, 2012


On dry pavement it is very easy to tell if you are in 4X; turn the steering wheel as far as it can go and drive a short distance. (obviously you want to do this in a parking lot or the like, not on the road). If the car turns smoothly, it is in two wheel drive. If it sort of "hops" or moves unevenly, it is locked in four wheel drive.

In normal driving conditions 4x doesn't feel any different than 2x.
posted by ook at 11:39 AM on January 15, 2012 [1 favorite]


What kind of car is it? It might not be true 4WD, especially if it is really a car and not a truck or SUV.
posted by narcoleptic at 12:03 PM on January 15, 2012


Well, I don't know much about 4WD, but my Jeep had a switch, and my gas mileage was pretty much more than halved when I used it, so I think that might be a quick way to tell!
posted by pazazygeek at 12:18 PM on January 15, 2012


The stomp-on-the-gas-on-dirt method may not be reliable. I once drove a Dodge Power Wagon that was "4-wheel drive," but only one front wheel at a time ever got power. If your observer was on the other side, the powered front wheel would be invisible. I think you want that indicator light fixed even if that's all that's wrong, because as noted, driving on dry pavement in 4WD is bad for it, and you want some way of knowing. In other words, you're going to need the mechanic anyway, unless you can fix the bulb or wiring or whatever yourselves.
posted by Kirth Gerson at 12:29 PM on January 15, 2012


Just to confirm that you have the correct answers, as far as my experience goes. In four wheel drive, all the wheels will slip on a slippery surface (well, maybe only one out of a pair as Kirth Gerson says - check both sides), the turning radius is decreased and going in a tight circle does feel "lumpy". Get the light fixed. Happy trails!
posted by Hobgoblin at 12:34 PM on January 15, 2012 [1 favorite]


A mechanic can put the car on the lift and tell you in like 10 seconds, for which there should be no charge.
posted by DarlingBri at 12:35 PM on January 15, 2012


The car is an SUV. Sounds like we need to get it checked. But now I am confused- if using the fwd in snow makes the wheels spin and loose control, when are you supposed to use it? I thought it was something you used when there was snow on the ground. Sorry to be dense; I'm just totally inexperienced about these things.
posted by foxy_hedgehog at 12:49 PM on January 15, 2012


I think the point is that if you stomp on the gas on snow then the powered wheels will lose traction.
posted by katrielalex at 12:53 PM on January 15, 2012


if using the fwd in snow makes the wheels spin and loose control, when are you supposed to use it?

The idea is if you stomp on the gas on a slippery surface any wheels that are powered will inevitably lose traction. If your car is engaged in 4WD (not FWD, that's front wheel drive,) all the wheels can/will spin. If your car is FWD or RWD, only one set of wheels will start spinning, because nothing is making the other two move. Putting a car in 4WD doesn't magically mean that the wheels won't spin. What it means is that if some of the wheels spin, you still have one or two that should hopefully gain enough traction to move the vehicle.
posted by InsanePenguin at 1:09 PM on January 15, 2012


Due to the vagaries of various 4wd systems the only real way to tell if the front axle is engaging is to put it on a lift and see if the system is physically engaging. Some systems are normally fwd and when you select 4wd it engages the rear axle(that age of Subarus have such a system), most are the opposite. Some have a system that lets them run just fine on dry pavement(once again Subarus and some Jeeps have this system and probably others). Unless you are fairly familiar with how the transfer case and differentials work in your car you are better off taking it to a mechanic and have them explain it to you. Also google your 4wd system on the internet to get an explanation so you have some basis for what your car is doing.

And lastly 4wd is great in low traction conditions if you know how to use it and its limitations. No matter what you are at the mercy of how much traction your tires can generate and the right tires make much more difference than most drivetrain configurations (tank tracks are great). Which is why 4wd mostly lets you get going on snow and ice but doesn't let you stop any faster (it can with certain driving techniques but ABS is much better and easier for most people to use). The SUV flipped over in the ditch during a snow storm is a cliche for this reason.

here are some quick links
posted by bartonlong at 1:26 PM on January 15, 2012 [4 favorites]


Due to the vagaries of various 4wd systems the only real way to tell if the front axle is engaging is to put it on a lift and see if the system is physically engaging. Some systems are normally fwd and when you select 4wd it engages the rear axle(that age of Subarus have such a system), most are the opposite. Some have a system that lets them run just fine on dry pavement(once again Subarus and some Jeeps have this system and probably others). Unless you are fairly familiar with how the transfer case and differentials work in your car you are better off taking it to a mechanic and have them explain it to you.

This. Even the test of going out to the icy parking lot and stomping on the gas won't tell you much if your car has traction control that won't allow wheel spin, for example. There are too many possible systems out there for us to guess and give you an abstract answer.
posted by Forktine at 1:45 PM on January 15, 2012


I once drove a Dodge Power Wagon that was "4-wheel drive," but only one front wheel at a time ever got power.

This is normal. Traditional 4WD doesn't really mean "four wheel drive", it means "both axles are powered". Each axle has a differential gear which shifts power between the wheels on that axle;
this mechanism is what allows cars to go around corners without skidding.

When you are driving a 2WD car and you lose traction, only one of the wheels on the powered axle will spin. When you are driving a 4WD vehicle and you lose traction, one wheel on each axle will spin, and the other wheel will stay in place.

The point of 4WD is that you have power on both axles, so even if one set of wheels slips, it's likely that you still have power on the other set of wheels. As long as the vehicle keeps moving, it doesn't really matter if you lose traction sometimes.

The traditional solution to this problem is a locking differential, which lets you force both wheels on the axle to keep turning even if one of them is slipping. This is the same idea as 4WD but it works side-to-side instead of front-to-back.

Modern vehicles often have something called "automatic traction control" which is an electronic device that detects wheel slippage and fights it by engaging the brake on that wheel. By holding the slipping wheel steady, the car uses the differential to push power over to the other wheel. It accomplishes the same job as a locking differential.

Traction control and 4WD are orthogonal solutions to wheel slippage; my rear-wheel-drive convertible has traction control on the rear axle, but of course the front wheels are only for steering and not for power.
posted by Mars Saxman at 2:10 PM on January 15, 2012


You may only be able to put the vehicle in 4wd when it is stopped and in park or neutral. That may be why the light isn't lighting up.

You should be able to feel it while driving. The truck will feel more sluggish- won't accelerate as fast.
The car is an SUV. Sounds like we need to get it checked. But now I am confused- if using the fwd in snow makes the wheels spin and loose control, when are you supposed to use it? I thought it was something you used when there was snow on the ground. Sorry to be dense; I'm just totally inexperienced about these things.
This misconception is, unfortunately, why you see so many 4wd vehicles in the ditch when it snows. Basically, all 4wd does is make it a little harder to get stuck, and a little easier to get out if you do get stuck. It can give you more traction, but only to the extent the tires won't slip.
posted by gjc at 4:02 PM on January 15, 2012


Thanks everyone! Very helpful.
posted by foxy_hedgehog at 4:39 PM on January 15, 2012


Basically, all 4wd does is make it a little harder to get stuck, and a little easier to get out if you do get stuck.

It also gives you some cornering advantage on slick roads, at least compared to RWD vehicles. I inadvertently verified this with a Jeep I owned. It had a jointed front driveshaft that was supported in the middle by a ball bearing. I didn't know it, but the balls in the bearing had left the building, and the resulting oscillation would pull the transfer case out of 4WD with no warning or outward sign. I was driving at night on a very curvy and snow-covered road, doing fine, when the 4WD disengaged. At the next corner, I went into a spin and wound up parked off the road next to a large tree.
posted by Kirth Gerson at 4:53 PM on January 15, 2012


What ook said. When you turn a corner, the wheels need to spin at different speeds since some are traveling father then others. If you're in standard 4wd and try to turn on dry pavement, (where slippage would not normally occur) you'll get a jerking motion or feel some abnormal resistance to your turn.
posted by Dr. ShadowMask at 4:56 PM on January 15, 2012


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