AWD/4WD Explained

[CharBaby]

I'm not sure if this section is the optimal section for this subject but it can be changed by the Mod's if need be.

 

[dumkid]

4wd is typically heavier duty and can't be used on packed ground or pavement without it binding and causing wheels to slip. the front and rear axle are locked together, usually with a splined collar. awd is just 4x4 for soccer moms and has clutches to eliminate the binding and hopping on pavement, but the clutches can also slip when you need them to drag you out of a sandy hole and the back wheels don't have traction. jeep calls their awd system 4x4 when it's an open center diff (I think it's lockable though) and doesn't have a 2wd mode. there's also AWD like some old Mitsubishis, where the center diff is like an actual differential with a limited slip instead of being primarily front or rear wheel drive with clutches to put a little bit of power to the other axle so you don't get stuck on wet grass. many 4x4 systems the front driveshaft and differential don't spin in 2wd because of locking hubs or an axle disconnect, and in an old fashioned 4x4 system there's no clutches to slip and no electronics, just a stick that engages the front driveshaft and locking hubs. i like the mechanical system, and i replaced a few electronic 4x4 systems with mechanical ones. the electronic systems i replaced are basically just a normal transfer case controlled by a computer so you can't grind gears and break stuff by shifting into 4low at high speed.

tldr: awd is for soccer moms and people who live in snowy places. 4x4 is heavy duty AWD and can sometimes get you out of places where an awd would be stuck. very few people need awd or 4x4, although it's nice in sand and snow

 

[pantygnome]

4wd is typically heavier duty and can't be used on packed ground or pavement without it binding and causing wheels to slip. the front and rear axle are locked together, usually with a splined collar. awd is just 4x4 for soccer moms and has clutches to eliminate the binding and hopping on pavement, but the clutches can also slip when you need them to drag you out of a sandy hole and the back wheels don't have traction. jeep calls their awd system 4x4 when it's an open center diff (I think it's lockable though) and doesn't have a 2wd mode. there's also AWD like some old Mitsubishis, where the center diff is like an actual differential with a limited slip instead of being primarily front or rear wheel drive with clutches to put a little bit of power to the other axle so you don't get stuck on wet grass. many 4x4 systems the front driveshaft and differential don't spin in 2wd because of locking hubs or an axle disconnect, and in an old fashioned 4x4 system there's no clutches to slip and no electronics, just a stick that engages the front driveshaft and locking hubs. i like the mechanical system, and i replaced a few electronic 4x4 systems with mechanical ones. the electronic systems i replaced are basically just a normal transfer case controlled by a computer so you can't grind gears and break stuff by shifting into 4low at high speed.

tldr: awd is for soccer moms and people who live in snowy places. 4x4 is heavy duty AWD and can sometimes get you out of places where an awd would be stuck. very few people need awd or 4x4, although it's nice in sand and snow

The "4wd" in my RAM 1500 begs to differ It uses clutches and a ball/ramp setup to engage them with an encoder motor to apply varying levels of pressure based on what the various computers *think* you need.

The funny thing is, the hardware is stout and could last a very long time (even the clutches) but Mopars terrible s/w programming put it in a state where the ABS, traction control and ball/ramp engagement all fight each other. Leading to a constant on-off-on cycle under the right (wrong) conditions. Then the clutches overheat and need to be replaced.

You can't fully disable traction control, and you cant disable ABS at all. Someone actually "fixed" the issue with a switch you wire in that gives the encoder motor "full send" which gives 100% clutch engagement. All the issues disappear and the system works really, really well.

I long for the chain driven mechanical linkage xfer case that was in my old Nissan Frontier.

 

[totegoat]

I enjoy both.

 

[pantygnome]

The AWD setup in my G37 is actually quite good.

AFAIK it runs as 100% RWD (or 99%/1%) until the front wheels slip, at which point a pump transfers fluid under high pressure to the front diff to engage it. Computer samples at 10 times per second. Its basically the system from the previous generation GT-R, put into an Infiniti. The current gen GT-R does it even better, 100 times per second sampling and it can control the front left and right independently.

There is definitely a bunch of ways to skin the cat, some are better than others (depending on what you want...I prefer performance, so the G37/GT-R setup are ideal).

 

[dumkid]

The "4wd" in my RAM 1500 begs to differ It uses clutches and a ball/ramp setup to engage them with an encoder motor to apply varying levels of pressure based on what the various computers *think* you need.

The funny thing is, the hardware is stout and could last a very long time (even the clutches) but Mopars terrible s/w programming put it in a state where the ABS, traction control and ball/ramp engagement all fight each other. Leading to a constant on-off-on cycle under the right (wrong) conditions. Then the clutches overheat and need to be replaced.

You can't fully disable traction control, and you cant disable ABS at all. Someone actually "fixed" the issue with a switch you wire in that gives the encoder motor "full send" which gives 100% clutch engagement. All the issues disappear and the system works really, really well.

I long for the chain driven mechanical linkage xfer case that was in my old Nissan Frontier.

id still consider that an AWD system, even though it's marked as 4x4 and plenty strong. just my .02

 

[D60]

I didn't watch it and this has been beaten more than a dead horse. Just because someone made a video doesn't make their opinions true because there actually is no industry standard.

My opinion is simple:
AWD: center diff thus suitable for FT use
4wd: no center diff thus can bind and not suitable for FT use

Done.

 

[pantygnome]

id still consider that an AWD system, even though it's marked as 4x4 and plenty strong. just my .02

True. We can leave it in 2WD, though, so its not always on.

The system has 2WD, 4-Auto, 4-Lock and 4-Low.

4-Auto and 4-Low do what they say, but 4-Lock acts pretty much the same as 4-Auto because of the crappy programming. If 4-Lock actually locked the truck in 4WD, it would be much better.

 

[D60]

id still consider that an AWD system, even though it's marked as 4x4 and plenty strong. just my .02

Nope (IMO) because when it's truly mashed the clutches together it'll bind. No center differential

But see, that's where it gets muddy because it can modulate the clutches to kinda sorta simulate a diff (if you're willing to define slippage as similar to differentiation).

And this is why no video or "authority" will ever be right. Or wrong.

Next I'd like to discuss if those fire trucks are bright yellow or green?? !!

 

[D60]

True. We can leave it in 2WD, though, so its not always on.

The system has 2WD, 4-Auto, 4-Lock and 4-Low.

4-Auto and 4-Low do what they say, but 4-Lock acts pretty much the same as 4-Auto because of the crappy programming. If 4-Lock actually locked the truck in 4WD, it would be much better.

Fear not, the NP246 in GMT800's is just as bad.

Just yesterday I was doing a standard LH turn at an intersection in my parents' 2006 Silverado and thought the transmission was slipping. It started to strain more and random groaning was occurring and I needed more accelerator.

The average driver doesn't notice but I do. I saw my mom had left it in 4Auto and it was inexplicably trying to engage 4wd in a slow turn on dry pavement. Once I saw that button lit up I realized it was just binding in the intersection.

My old '05 Yukon used to behave EXACTLY the same.

 

[pantygnome]

Fear not, the NP246 in GMT800's is just as bad.

Just yesterday I was doing a standard LH turn at an intersection in my parents' 2006 Silverado and thought the transmission was slipping. It started to strain more and random groaning was occurring and I needed more accelerator.

The average driver doesn't notice but I do. I saw my mom had left it in 4Auto and it was inexplicably trying to engage 4wd in a slow turn on dry pavement. Once I saw that button lit up I realized it was just binding in the intersection.

My old '05 Yukon used to behave EXACTLY the same.

The funny thing is the xfer case itself is pretty beefy. And those who have the "workaround switch" have been using it for years fully locked and never an issue...but, they know when and when not to have 4WD engaged.

Just gives evidence to the idea that stuff like this exists because people are oblivious to using their vehicles correctly.

Me, I dont need the manufacturer to save me from myself. I know how to use my stuff the right way.

I've actually considered trying to sniff the CAN bus to see if I can hijack the message that tells the encoder what %-age to engage, then just tell it to engage at 100% all the time

 

[4WD]

Have owned, modified, and studied many - and must say very few are alike …
Even the 3 in my signature are unique … Owners need to read that book in the glovebox …

 

[Owen Lucas]

Unless you're going "mud boggin" I think 99% of the population doesn't need the ole' fashioned 4x4 tech, it's been replaced and upgraded beyond recognition for a reason.

 

[missingcurlybracket]

As noted in the video the difference is marketing but he does go into different layouts often associated with either one.

I’m just going to use this to soapbox about how Kia/Hyundai’s AWD courtesy Magna Powertrain (electrohydraulic clutchpack in between rear diff and prop shaft) is quite solid but has an interesting trade off.

AWD actuation is proportional to throttle so flooring it gives you the most AWD action - great for surefootedness in slippery conditions or quick, sharp turns while keeping front wheelspin away, but less optimal for long-term wear as it is used more and slips with throttle application while turning.

There’s an AWD Lock (or more accurately, “more AWD please”) button that approximates 4Hi by increasing the base AWD clutch pressure modifier and is nice to have - it is indeed capable of donuts in snow, or as much as a FWD-biased AWD crossover can be - but my approach angle is more of a constraint.

The AWD coupler part is the same in the past decade ish of Sportage, Sorento, Tucson, Santa Fe (subject to specifics) from the base 2.4L I4 up to the 3.3L V6 so it’s reasonably stout in my application. Was just replaced at ~118k miles and I did subject it to sand, towing, above snow abuse, etc. - I expect the new part to live a little cushier life - but regrettably it is designed as a lifetime sealed part. Transfer case and rear diff oil can be changed, but not easily for the AWD clutchpack. It likely needing to be 100% filled doesn’t help.

I did read a post about a guy DIY-ing a drain port (drilled) for the similar part in his Kona and it did have a fluid specced, but no mention in the manual here other than posts stating Shell TF0870(?) or Redline MT-LV(?)

But yea, for my uses it’s a great single-clutch AWD system. Shame the engine and anti-theft didn’t get as much love.

 

[4WD]

Unless you're going "mud boggin" I think 99% of the population doesn't need the ole' fashioned 4x4 tech, it's been replaced and upgraded beyond recognition for a reason.

True - I own one of the few that can lock all 4 or other combinations … However it’s not made for snow over roads …
Newer Wranglers now have that option - but only time will tell if you give up durability etc …

 

[D60]

Unless you're going "mud boggin" I think 99% of the population doesn't need the ole' fashioned 4x4 tech, it's been replaced and upgraded beyond recognition for a reason.

As a Luddite these arguments scare me.

I want 100% control. I want a lever that moves a mechanical linkage. I want a drivetrain that binds in 4wd on high traction surfaces, or a reliable, durable center diff that I can lock. I want a 2 speed transfer case.

I know I'm in the minority.

 

[edyvw]

AWD system is sufficient for 99.99999% of people who actually need torque on all wheels. In snow t is generally better as it is lighter, more efficient and in the end, it depends more on tires. Many tourists here in CO realize very fast that Tahoe with 4WD doesn’t get you far in snow storms.
AWD in cars like BMW I have is also far better proposition. It is 40/60 split but on track system shifts to 20/80%. New BMW’s in some models can be turned off.

Off roading etc. 4WD. There is no doubt about that.

 

[WeyounDS9]

I have whats called the "upgraded" 4x4 transfer case in my 4x4 2008 Pathfinder.
To thr 4HI, 2WD and 4 LO options it adds "auto" to allow the transfer case to open via clutches for on pavement use (rain/snow etc)

 

[Thermo1223]

4wd is typically heavier duty and can't be used on packed ground or pavement without it binding and causing wheels to slip. the front and rear axle are locked together, usually with a splined collar. awd is just 4x4 for soccer moms and has clutches to eliminate the binding and hopping on pavement, but the clutches can also slip when you need them to drag you out of a sandy hole and the back wheels don't have traction. jeep calls their awd system 4x4 when it's an open center diff (I think it's lockable though) and doesn't have a 2wd mode. there's also AWD like some old Mitsubishis, where the center diff is like an actual differential with a limited slip instead of being primarily front or rear wheel drive with clutches to put a little bit of power to the other axle so you don't get stuck on wet grass. many 4x4 systems the front driveshaft and differential don't spin in 2wd because of locking hubs or an axle disconnect, and in an old fashioned 4x4 system there's no clutches to slip and no electronics, just a stick that engages the front driveshaft and locking hubs. i like the mechanical system, and i replaced a few electronic 4x4 systems with mechanical ones. the electronic systems i replaced are basically just a normal transfer case controlled by a computer so you can't grind gears and break stuff by shifting into 4low at high speed.

tldr: awd is for soccer moms and people who live in snowy places. 4x4 is heavy duty AWD and can sometimes get you out of places where an awd would be stuck. very few people need awd or 4x4, although it's nice in sand and snow

That's a bias over simplification...

My Subaru's AWD got me out of and into places I've watched full size trucks get stuck in. Tires has 100% more to do with whether you get stuck or not.

AWD is not for soccer moms any more than 4WD is bro trucks who think they can offroad.

 

[4WD]

AWD system is sufficient for 99.99999% of people who actually need torque on all wheels. In snow t is generally better as it is lighter, more efficient and in the end, it depends more on tires. Many tourists here in CO realize very fast that Tahoe with 4WD doesn’t get you far in snow storms.
AWD in cars like BMW I have is also far better proposition. It is 40/60 split but on track system shifts to 20/80%. New BMW’s in some models can be turned off.

Off roading etc. 4WD. There is no doubt about that.

Lots to do with the tourists - one of my engineers owns 2 Rubicons and a Yukon AT4 … The Yukon gets the call after a heavy snow. (Auto mode+winter tires) … Only the newer Rubicon’s have something similar …
They don’t change tires on the Jeeps …