4x4 explanation please

My first 4x4...

I put my 2010 AC in 4H and did a slow, tight 360 in a large paved parking lot. The outside wheels seem to brake ~2 seconds and then accelerate ~2 seconds. There was a rubber tire chirp each time it accelerated. Same behavior in 4H.

I'm curious what is happening here. There seems to be some kind of electronic control. I also noticed there was a resistance in the steering in 4WD which I had not noticed in the dirt.

 

Stop doing that on pavement, please. Your truck and wallet will be much happier.

 

Yeah best that you don’t do that on paved surfaces- especially in 4L!!! You can break a CV or something worse. You can drive on hard surfaces in 4H but turning should be avoided - especially “tight” turns.

 

Your truck is binding. Do not engage your 4wd on dry paved surfaces.

 

This is a very common mistake on 4x4 as the Tacoma is part-time only for off-road or very slippery surfaces. The binding you are feeling is the front tires turning at different speeds/rates as the outer tire is travelling further (larger circle) so the inner has to hop or skip as all 4 wheels want to be going the same speed. Full time systems like the limited four runner has have an auto setting for on pavement ops as it has an additional differential in the transfer case. AWD also have this but most are full time always on and computer controls the torque splits. Google 4x4 systems for full detailed explanations.

 

This outside tire is traveling further than the inside tire and the truck is trying to power both close to equally so you get that chirp and binding. Worse with lockers. Not a great idea on pavement as others have stated.

 

Jesus, I remember watching my buddy do this in his Toyota Landcruiser in high school and destroy his differential.

I know the noise you are talking about and it is an unholy, God-awful chirp crunch noise no automobile in working order should ever emit.

Four wheel drive means all four wheels turning at the same rate at the same time.

When you are in two wheel drive and go around an inside corner, the two driver-side wheels will travel slightly less distance than the two passenger-side wheels, due to their path being on the outside of the curve.

Think about a track foot race where the runners all get set at different spots but end up at the same finish line. It's the same concept.

However, you had all four wheels locked together, mechanically. That mechanical lock would not allow the tire to rotate and basically is fighting the traction of the tires to see which won.

You sound like you got lucky and your truck won this one. My buddy lost.

I will warn you though that we didn't realize the damage until a bit later, so you might want to get that checked out sooner rather than later.

I don't know how to check it yourself. Luckily I learned from my buddy's costly mistake and have never had to check, knock on wood.

But his was also a Landcruiser, any repair on that thing is more costly. Even if you torched yours it'd be cheaper to fix I bet.

Good luck regardless.

 

I read one should engage 4WD now and then if it is not in regular use. Fortunately it was only driven around 100' at essentially idle speed. What are the parts that get damaged? Is it the CV as someone suggested?

Don't these (TRD Sport) have a limited slip differential? Is that disabled in 4WD?

If the 4WD turns the wheels at the same speed, what does a locking differential do? I thought the locking differential locked the two wheels into the exact same rotating speed and that is the advantage of the OR model.

>>>However, you had all four wheels locked together, mechanically. That mechanical lock would not allow the tire to rotate and basically is fighting the traction of the tires to see which won.<<<

Literally, all four wheels are locked into the same speed even if one or more have no traction?

Thanks for these informative answers and warnings. I have been an amateur wrench and car/bike guy all my life. Mostly motorcycles. Just never owned a 4x4. I hope to hook up with some SOCAL locals to learn some lessons on off road driving since I don't really have a clue.

 

Back in the day this was never a problem. Everybody knew that operating in 4X4 in surfaces with good traction was a serious no-no. But during the 1970's all of the truck manufacturers started making what they called at the time "full time 4X4". It was essentially what we call "All Wheel Drive" today. But they came with a switch, or lever that allowed you to lock the transfer case into true 4X4. That, and the proliferation of AWD vehicles today have confused drivers who don't understand the difference.

And doing it can be an expensive mistake. In college I owned a 1975 Jeep truck with full time 4X4. I was smart enough to know not to lock the transfer case, but not experienced enough to realize I had a problem until it was too late. At some point the vacuum hoses between the transfer case and switch had gotten reversed. While I had the switch in the unlocked position, I was driving locked in 4X4. I had to pay to have the transfer case rebuilt twice in 3 months before we figured out the problem.

 

Nope. If you cut hard enough to the side, the front wheel is traveling faster / more than the rears

 

On my Jeep the drive chain was stretching due to the strain. Over time it became so loose that it would slip on the gears when pulling away from a stop. I'd get pop, pop, sound and you could feel the truck stop moving when the chain slipped. I've also seen universal joints break as well as the front drive shaft.

In my case it wasn't a sudden failure, but something gradual over time.

 

Here’s a good explanation

If you don’t speak Ausie, and don’t mind a dry explanation

 

4WD and AWD are not the same.

AWD has some sort of center differential that allows the front and rear axles to rotate at different speeds....such as when turning. Wheels following different paths turn at different speeds....hence the term "differential".

4 wheel drive lacks a center differential. This means the front and rear axles always rotate at the same speed. In low traction situations that's fine. Absolutely not on high traction surfaces, though.

There are hybrid systems that can incorporate both characteristics. But that's another thread.

You should engage the 4x4 system periodically to maintain it's function. If you are left with no choice but to do this on a paved road....just make sure you drive in a straight line only.

 

What the other guys were talking about regarding the difference in tire spin is taken care of by the differentials for the most part. The problem comes in your transfer case, because there is no diff in there. When you turn, all 4 tires take a different path, not just an inner and outer path. You mentioned lockers, and you were right about what they do. You just have to think of your transfer case as permanently locked. The front and rear driveshafts HAVE to turn at the same rate, and when you turn they are trying to rotate at different rates causing those terrible noises you mentioned. To keep turning at the same rate, either a tire has to slip, or a part has to break. This is why it's ok to let the tire slip a bit when on low traction surfaces like silt, gravel, mud, etc, but when you have traction, the truck would rather break parts than let the tire slip. Key take away, never use 4wd on pavement unless you are only going straight.

 

Yes your four wheel drive needs exercise.
A straight line or real gentle turns are ok.
Long story short not sure if it’s been told?
In 4 the drivers side and passengers side are trying to turn at the same speed.
While turning the circle one side needs to travel at a different rate then the other.
The inner circle is smaller than the outer one.
Puts a lot of stress on other components.
Using the the 4 wheel options Keeps actuators working and lubes stuff.

Lol I type slow!

it’s been said.
I use 4 often in the winter and disengage it to pull in/out of the garage.
It lets me know if it doesn’t like what I’m doing.

 

That is a bit of an oversimplification. In 2wd power is only being sent to the rear wheels. But when you go around a corner all 4 wheels are taking a different path and turn at different speeds. The outside rear has the greatest distance to gravel and must turn fastest. The inside front wheel has the least distance to travel and will turn slower. Since the fronts are coasting and power is ony going to one rear wheel this is easy.

Your rear differential will only send power to ONE rear wheel during turns to prevent damage. If you have a locking diff you can lock it to force both to turn at the same speed. But should only be locked in extreme low traction situations.

When you shift into 4X4 you are still only getting power to one front and one rear unless you have the diff locked. Some vehicles will allow you to lock both front and rear. But even at that when you corner the one front and one rear are fighting each other. In a low traction situation the wheel that is has the least distance to travel will slip on the ground without damage. If traction is good you risk damage


AWD uses computer technology to send power to all 4 wheels and still allow them to turn at different speeds. It works great in light snow, wet pavement, and light mud. But in extreme situations it is overwhelmed and doesn't work as well.

4x4 is a simpler old school system. The only time I can think of where use on pavement is acceptable is a wet boat ramp. And then only in a straight line and for just long enough to get the boat out. Do not use on rainy roads or even light snow except for limited use just to get moving. If the snow is over 2-3" deep and there are no clear patches OK.

And yes it is very important to take it out onto a dirt/gravel road once every month or so and get in a few miles in 4X4. The owners manual suggests 10 miles/month. Some months I may drive several hundred miles in 4X4. Sometimes I'll only get 2-3 miles and occasionally I'll skip a month. But if you don't use it regularly you will have problems.

Limited driving (10-15') on pavement in a straight line is OK. But not much more and you're not going to get in your 10 miles/month safely on pavement. Find a dirt or gravel road.

 

So when you're driving and it's snowy out, would you just switch back and forth between 2WD and 4HI, using 2WD when making turns and 4HI when going straight? What about highway driving? When there are bends in the highway, can you switch frorm 4HI to 2WD?

 

If I think that I have little enough traction to need 4wd, then I'm not going highway speeds.

Around town, I'll switch in and out. More out than in, until I get to a hill or something where traction is a concern.

On dirt, put it in 4 and forget about it.