4WD confusion

[alaskaman]

This thread reminds me that Toyota engineers it's 4WD systems with a reason. That being the driver has options to deal with road conditions.

4Hi allows you to have the stability at higher speeds say during a commute. 4LO allows you to pull and push slowly with increased torque to get through very tough roads using very low speed.

Locking the differential allows you to track in deep snow mud with better control of your vehicle. It gives the driver more road feel and control of the truck and is my favorite for Anchorage winter. But here's the deal. Some feel better with the fancy ATRAC ON and some (me) feel better with it OFF.

It really depends on what you want. A caveat however is this. Ice and snow at varying road temperatures are tricky....so slow down and try different modes at the correct speeds.

Finally none of these work well without excellent tires. Do your research and if you live in a snowy climate get some dedicated winter tires to complement the superior 4WD system we know and love.:driving:

 

[Lolrax]

Perfect, thanks.

Also make sure to use your center diff lock when there is snow on the ground! You can activate it while driving until about 35MPH and if there is snow on the ground you can turn and do all the stuff you want.

When you get into a parking lot or are on dry pavement shut it off. It makes a world of difference.

 

[M1911]

No, it doesn't kick on the AWD. It is sending power to all 4 wheels all of the time but the differential is open so you can drive around however you want.

Minor quibble -- the center diff is limited slip, so it isn't an "open" diff.

Systems that kick on the AWD almost always kick it on way too late for it to be useful.

I agree completely.

I leave mine on from basically October-April here in Canada.

I have the V8, so it is always in 4WD.

 

[m85476585]

Also make sure to use your center diff lock when there is snow on the ground! You can activate it while driving until about 35MPH and if there is snow on the ground you can turn and do all the stuff you want.

When you get into a parking lot or are on dry pavement shut it off. It makes a world of difference.

I disagree. For snowy roads, there is plenty of traction with the center unlocked. You'll get much less understeer and have more predictable handling with it unlocked. Locking it is good for getting unstuck, or going through deep stuff, or off-roading.

I went for a drive on some muddy/snowy dirt roads with a friend who had a Tacoma with a traditional transfer case. He couldn't keep up with me on the corners because his would understeer if he took the corners at speeds I was taking them at. I've also tested both locked and unlocked on snowy roads and parking lots. I noticed the same thing, and that eliminates any variables like different tires or vehicles. Try it for yourself and see which one you like better.

It's not that great in my '03. Perhaps it has gotten better in later years.

If I was going to do significant offroading in my '03, I'd put in an ARB rear diff. I take mine out on the beach, but that is not very challenging.

ATRAC might take some getting used to, and I'll admit I haven't used it much, so I don't have a lot of experience with it. But I like to test things out when I can. I've noticed that it works best if you give it a steady amount of gas and let it do the work, loudly hammering on the brakes. It works slowly, but it should get you moving. It does not want you to spin the wheels, so don't try to floor the gas and overpower it. I've also noticed that it might stop working if you have one foot on the brake and the other on the gas (for example, starting on a steep hill (HAC is useless)), but I haven't been able to test that again to confirm.

For what I do, ATRAC is good enough that ground clearance is the biggest limitation to where I can go. I would need a lift, bigger tires, and armor before I would consider getting a rear locker. But I decided it's not worth spending that much to modify my truck right now, so I'll probably keep it all stock for a while.

 

[M1911]

I disagree. For snowy roads, there is plenty of traction with the center unlocked. You'll get much less understeer and have more predictable handling with it unlocked. Locking it is good for getting unstuck, or going through deep stuff, or off-roading.

Agreed. When you lock the center diff in snow the truck gets very tail happy. I drive in snow a lot here in the Boston area. The only time I lock my center diff in snow is if I'm going into some very deep stuff. If a few inches of snow are covering the road, I leave the center diff unlocked.

 

[Lolrax]

I disagree. For snowy roads, there is plenty of traction with the center unlocked. You'll get much less understeer and have more predictable handling with it unlocked. Locking it is good for getting unstuck, or going through deep stuff, or off-roading.

I went for a drive on some muddy/snowy dirt roads with a friend who had a Tacoma with a traditional transfer case. He couldn't keep up with me on the corners because his would understeer if he took the corners at speeds I was taking them at. I've also tested both locked and unlocked on snowy roads and parking lots. I noticed the same thing, and that eliminates any variables like different tires or vehicles. Try it for yourself and see which one you like better.

Interesting, I love having the locker on in heavy snow or snowy roads. The absolute best time for it is when you're going near highway speeds and change lanes and cross that "snow hump". With the center lock on, it doesn't seem to make the car as squirrely crossing the hump. I have always felt way more in control with the center lock on.

I also like how it disables traction control because I can burn out of whatever I need without having the nanny shut me down.

Agreed. When you lock the center diff in snow the truck gets very tail happy. I drive in snow a lot here in the Boston area. The only time I lock my center diff in snow is if I'm going into some very deep stuff. If a few inches of snow are covering the road, I leave the center diff unlocked.

I know what you're saying about it getting tail happy, but I just feel much more in control with it on especially at higher speeds in snow. Then there is also the issue where the traction control is off with the center diff locked, which allows me to get out of my own way.

 

[alaskaman]

I disagree. For snowy roads, there is plenty of traction with the center unlocked. You'll get much less understeer and have more predictable handling with it unlocked. Locking it is good for getting unstuck, or going through deep stuff, or off-roading.

The only thing I can say is that having the diff locked gives me more control of the truck without all the fancy tech kicking in and telling what I already know :hungry:

 

[m85476585]

It sounds like having it locked increases stability at highway speeds when you are mostly going straight. That makes sense.

I tend to drive on mountain roads in the winter, and in that case having it unlocked lets me take turns faster. And I like having VSC on because it lets me push it a bit but kicks in if I go too fast. It saved me from sliding into a guard rail coming down a mountain pass last winter, but if I didn't have it I would have been driving more cautiously in that case.

 

[M1911]

It sounds like having it locked increases stability at highway speeds when you are mostly going straight.
.

No, not at all. Seriously.

 

[m85476585]

This is funny, it sounds like there are 3 (somewhat) contradicting opinions.

M1911 says having the center locked makes it tail-happy (oversteer?)
I say having it locked it makes it understeer in turns
Alaskaman and Lolrax say it improves control and stability

Luckily we have options, so try it for yourself and see what you like best.

 

[M1911]

This is funny, it sounds like there are 3 (somewhat) contradicting opinions.

M1911 says having the center locked makes it tail-happy (oversteer?)
I say having it locked it makes it understeer in turns
Alaskaman and Lolrax say it improves control and stability

On high-friction surfaces, having the center diff locked will result in understeer.

However, locking the center diff also disables traction control. On low-friction surfaces (like snow), that makes it easy to break traction. Since the rear is a lot lighter than the front, the rear wheels break traction before the front, giving you oversteer. Try this on a snow covered parking lot: with the center diff locked, turn the wheel a bit, then hit the gas with some enthusiasm. The rear will come around very quickly.

Now I grew up in Chicago driving rear-wheel-drive cars, mostly with manual transmissions. I'm quite used to hanging out the back around a corner in the snow. I was quite comfortable balancing oversteer with countersteering.

But when the 4Runner tail steps out, it does so quite quickly, and then spin control abruptly shuts off all the fun. Perhaps it would be easier to manage if spin control could be turned off. As it is, I prefer to just leave the center diff unlocked in the snow.

 

[rooost]

Yes, you can leave it in 4Hi all the time. There is a limited slip center differential, so it mechanically/automatically distributes power, which is faster than electronic systems on some vehicles that have to sense slipping first. It also has electronic control in case there is too much slipping for the LSD to correct, in which case it will pulse the brakes to the slipping wheel(s) to help send power to the ones with traction. It works well, and it's similar to the AWD found in high end cars such as some Audi Quattros.

Audi Quattros, I knew I had a bad ass sports car! Thats how I drive it good to know the mechanicals are up to it, now If I could just lower that CG

 

[KidVermicious]

This thread makes me want to shove my head in a blender.

Well yes - but most people don't understand it to that depth. Was easier to just compare it to AWD.

Was also COMPLETELY AND UTTERLY WRONG, but hey, don't let that get in the way of you wanting to sound like you know what you're talking about.

 

[nevada]

This thread makes me want to shove my head in a blender.



Was also COMPLETELY AND UTTERLY WRONG, but hey, don't let that get in the way of you wanting to sound like you know what you're talking about.

meh. based on what I found out yesterday, I would certainly call our 4runners AWD. until you lock the center diff at least.
full time 4wd is just that, FULL time. ours are not.

 

[KidVermicious]

meh. based on what I found out yesterday, I would certainly call our 4runners AWD. until you lock the center diff at least.
full time 4wd is just that, FULL time. ours are not.

AWD doesn't have a transfer case though. Full time 4WD doesn't mean it HAS to be in 4WD all the time, Full time just means it CAN be in 4WD all the time.

 

[nevada]

AWD doesn't have a transfer case though. Full time 4WD doesn't mean it HAS to be in 4WD all the time, Full time just means it CAN be in 4WD all the time.

AWD does have a transfer case. it has to. it may not have low range though....

 

[BlackWorksInc]

AWD doesn't have a transfer case though. Full time 4WD doesn't mean it HAS to be in 4WD all the time, Full time just means it CAN be in 4WD all the time.

Yes and no.

AWD has a "Transfer Case" as the part may be labeled. But it is little more than a 3rd differential. Where as what we commonly think of as a "Transfer Case" on a 4WD vehicle is a typically chain driven gearset with at minimum 1~2 gear reduction sets.

 

[KidVermicious]

AWD does have a transfer case. it has to. it may not have low range though....

You're right, poor choice of words on my part. AWD doesn't have a transfer case with a reduction section, which is what makes the difference between AWD and 4WD imo.

Except now that I think on it, my International Scout does say "All Wheel Drive" on the side... :roadkill:

 

[C.Rocks]

Well yes - but most people don't understand it to that depth. Was easier to just compare it to AWD.

For someone who doesn't know much at all about cars, BlackWorksInc's explanation was very clear and informative

Yes and no, I just want to clarify this point because it is often confused on this forum with newer members (not picking on you, it's just something that does pop up from time to time.)

The 4th Gen 4Runner in particular is a 4WD vehicle, it comes in two flavors of 4WD. Part-Time 4WD which means you can switch between 2WD, 4Hi, and 4Lo (all V6 4WD units are equipped with Part-Time 4WD,) the other option is All-Time 4WD (all V8 4WD units are equipped with this.) The biggest difference between the two is the that Full-Time 4WD does not have a 2WD option. It basically means that the V8's are always in 4Hi (the V6 will drive exactly the same as the V8 in 4Hi and it is perfectly okay to use it in daily driving as many members do.)

The main distinction I want to make here is mainly between AWD & 4WD (they do drive similar, but they are two completely different systems.)

All-Wheel Drive means that there is only a single stage transfer gearset (basically all it is is a secondary differential that shifts some power to the other axle as well.) An AWD vehicle is typically either FWD or RWD biased with some power distributed to the second axle; the "transfer case" is little more than a very small gearset attached to the end of the transaxle or transmission.

A 4WD vehicle has at minimum a 2 stage Transfer Case (often chain driven) that allows you to further change the gearing of the vehicle when in 4WD. This means that your final drive ratio is modified by selecting what transfer case position you want, (i.e. in 4Lo your gearing is so low in a 4th gen you cannot really go about about 30~35mph)

This is something that an AWD vehicle does not have the capability to do, not to mention the system is not as robust/stout enough to handle the type of low speed torque required to do some off-roading (which is why you have a 4Lo gearset to begin.)

Additionally all North American (basically all US model) 4th Gens come with a T3 Torsen Center Differential that allows torque distribution without binding up the 4WD system. This basically means that the vehicle can be driven in 4Hi on the road with minimal to no impact on driving characteristics (where as say a Jeep or other Domestic vehicle with a Part-Time 4WD system will bind and skip in turns when trying to drive on-road.)

Thank you for this! Just cleared up a lot of questions I had about AWD vs 4WD