4WD? AWD?

Guest · Jan 7, 2005

Hey there...

I know this is probably an often-asked question, buried in a FAQ somewhere, but I couldn't dig up an answer so I thought I'd post here.

About 6 months ago I bought a manual transmission 2002 with a 4WD badge on the back, and I've been wondering since I got it, how does the 4WD work? Without any kind of button/switch/lever in the cockpit to switch it to 4WD, it must be full-time. But full-time 4WD doesn't really exist, because to have 4 evenly powered wheels at once kills the handling. So it must be one of those "shifting the power from the wheels that slip to the wheels that grip" all-wheel-drive systems.

But then again, many "all-wheel-drive" systems aren't really "all-wheel". My car before this was a Subaru Outback, and one day I got hung up on a snowbank and watched as the 2 wheels in the air (diagonally opposite) spun in the air while the wheels still on the ground did nothing...turns out their version of all wheel means "one front wheel and the opposite rear wheel", which they should at best call "all axle drive".

So anyway, how does the power-to-the-wheels system work on the Rav4?

RAVMAN · Jan 7, 2005

From the RAV4 FAQ - http://ralphb.net/RAV4FAQ.html

------------------------------BEGIN------------------------------------------------

Subject: 3.1.3) How does the Four Wheel Drive (4WD) system work?

Very well

Actually, it depends on your choice of transmission, and whether you have the Limited-Slip Differential (LSD) option. See the Traction Adding Devices FAQ < http://www.a1.nl/phomepag/markerink/diffs.htm >
for more general information on these types of devices.

If you have a 2-Wheel-Drive RAV4, then it is powered by the front wheels only.

If you have 4WD, a full-time system puts power down to all four wheels at all times. Some refer to this as an "all-wheel drive" system, rather than 4WD, but AWD usually refers to "reactive" systems that delay transfer of power until after slip is detected. The RAV4 drive system is most correctly called "Full-time 4 wheel drive." It is reported that 25% of the engine power is normally sent to each wheel.

- For automatic transmissions, there is a center coupling that detects wheel slip and gradually locks the front and rear axles as the slip increases. There are no driver controls for this feature.
- For manual transmissions, there is a center differential lock button on the dashboard that manually locks the front and rear axles. When engaging, an amber "C. Diff Lock" indicator lights on the dashboard. When disengaging, there will be a beeping sound until the center differential is fully disengaged; it may beep just once, or may beep for as much as a full minute (seems to beep longer when cold). Toyota recommends that it only be used only in difficult situations, and that the center differential can be damaged if used improperly.
- For 4WD vehicles, there is an optional rear LSD available. In 1996 and 1997 model year, it was available only on standard transmission models, but starting in 1998, the rear LSD is available in all 4WD models. This device is called a "Torsen-type" LSD by Toyota, and is one of the most sophisticated and effective types available. It automatically detects wheel slip by either rear wheel and redirects the most power to the wheel that is slipping the least. There are no driver controls required for this device.

------------------------------END--------------------------------------------------

The RAV4 4WD system was changed beginning with the 2001 version.... no more center lock button

The keeper of the FAQ (Ralph Becker) accepts updates. Anyone willing to write up a 4.2 update? :?

Guest · Jan 7, 2005

Riiiiiiight....I'd read that in the FAQ there, but since my '02 didn't have a button to push or a light on the dash, I figured they'd changed the system since the FAQ was created.

So for 2001 and on, did Toyota switch to the detective coupling for the manual transmission as well?

Jeff · Jan 7, 2005

The whole concept of whether to say a vehicle is 4WD or AWD has no official definition or guideline, it depends on the individual manufacturer. That is why Subaru can say their cars are AWD, while Toyota says the Rav4 is 4WD, even though they both use essentially the same type of system. However, there are generally accepted definitions that are used buy most people in the automotive community to differentiate the two sytems.

The generally accepted principal is that any system which uses all four wheels to drive the car, whether part-time or full-time, can be considered four-wheel drive (or 4WD). However, in order to distinguish part-time systems from full-time systems, the two systems are referred to as four-wheel drive (4WD) for part-time systems, and all-wheel drive (AWD) for full-time systems.

A part-time system (4WD) uses no central differential, so that both axles are locked together, in order to split the torque evenly between both axles. This is the traditional 4WD system used on SUV's and trucks, and needs to be manually engaged by the driver, either using a gearshift or switch. This type of system cannot be used under normal driving conditions (because of the binding between the axles when you make a turn), so it is meant for use mainly on loose surfaces or off-road, and at low speeds (less than 45mph).

A full-time system (AWD) powers all four wheels all the time, whether actively or passively, and does not need to be activated like a part-time 4WD system. This system has become popular over the past 20 years, being used on such cars as Subaru, Audi/VW, Volvo, and Toyota, among others. It is a system primarily used on cars instead of trucks because it has been traditionally regarded as being not as rugged as a part-time (4WD) system. These AWD systems can use an assortment of manual and/or automatic differentials to distribute the torque among the wheels. These differentials can be electronically activated (such as the central diff lock on the older Ravs) or automatic (like the limited-slip diff on the rear of some Ravs).

All Rav4's of any year are considered AWD even though Toyota calls them 4WD, because they use full-time four wheel drive systems.

As Kelly mentioned above, there were some changes to the Rav's 4WD system starting with the 2001 model year. The 4WD system on Ravs with automatic transmissions remained the same, and has not changed since the Rav was born. This system engages the rear wheels whenever it detects slippage in the front wheels, without the use of a viscous coupling.

It was the 4WD system on Ravs with manual tranmissions that was slightly modififed. Whereas the older manual Ravs used an open center differential that locked when activated by the CDL button, the newer Ravs used a viscous coupling type center differential, similar to what Subaru has used for years.

No driver input is required for either of these systems that are used one the newer Ravs.

Here is an article on how a visocus coupling works.
http://auto.howstuffworks.com/differential9.htm

How that answers some questions....

Guest · Jan 7, 2005

Great answer. Thanks for the explanation.

I, too, have plates stating "Live Free Or Die". Currently typing this post from my office in Manchester.

Mohit · Jan 8, 2005

I know auto RAV4.1/2s have 25% of power sent to each wheel but does this power automatically vary from front to rear if the front or rear needs more power?

Also, i thought with a part time 4WD you can drive in 4WD mode on sealed surfaces as long as you're in high range and not low.

Guest · Jan 8, 2005

I have a 2004 RAV4 (4.2 generation) with manual transmission. One of the dealers with whom I test drove the RAV4 back in June told me that power is evenly distributed among the four wheels (25% apiece) at all times. The RAV4 uses a different 4WD system than, say, the Matrix, whose rear wheels don't kick in unless the front wheels lose traction. I think the RAV4 shares the same 4WD architecture as the Highlander and the new Sienna.

Please correct me if I'm wrong.

Guest · Jan 8, 2005

I took a video of my Rav4 in the snow last winter flooring the gas and the front wheels and back wheels spun at the same time, except the rear wheels seemed to have a split second lag between the front tires.

JW · Jan 15, 2005

Rear LSD..

I have the rare limited slip rear end in my '01 automatic RAV. It's a blast in the snow, as you can get that rear end sliding around like an old rear wheel drive car! The fun doesn't last as long though, as the front tires are digging in and pulling hard too........

Guest · Jan 16, 2005

When I was researching the difference between the Honda CR-V and the RAV4, before settling on the RAV4, I came across an article which compared both. The CR-V is called "real time" 4wd which means the front wheels need to slip before the rear wheels engage. In the article, they took both over the same course, which included a stretch of beach. The CR-V got stuck but the RAV4 didn't. When I tested the CR-V I started from a stop sign on a hill with a little gravel and the front wheels span. Thus my decision to go with RAV4 (plus it's more comfortable and handles better)

Guest · Jan 16, 2005

JJ said:
When I was researching the difference between the Honda CR-V and the RAV4, before settling on the RAV4, I came across an article which compared both. The CR-V is called "real time" 4wd which means the front wheels need to slip before the rear wheels engage. In the article, they took both over the same course, which included a stretch of beach. The CR-V got stuck but the RAV4 didn't. When I tested the CR-V I started from a stop sign on a hill with a little gravel and the front wheels span. Thus my decision to go with RAV4 (plus it's more comfortable and handles better)

Thanks for your input. No offence to Honda (which also makes fine products, such as my dad's 2000 CR-V and the Element which I once seriously considered), but I'm glad you went with the RAV4. It seems like everybody else who makes a comparison between the RAV4 and the CR-V always picks the CR-V hands down, and I don't know why. Yes, the new CR-V is roomier and more powerful than the 2001-2003 RAV4s, but the RAV4 feels more brawny to drive (especially the 2004-05), at least in my opinion. 8) The suspension, height of seating, etc. (and, of course, the 161 hp engine in the 2004-05 models) all make the RAV4 funner to drive than the CR-V.

Anyway, on to the 4WD business...

I feel a major difference in handling when driving my dad's 2000 CR-V compared to my 2004 RAV4, like night and day, even on dry pavement (both of which are 5-speed manual). I try to rule out the difference in power, but still, the two vehicles just feel different, regardless of the difference in power. Maybe the fact that my RAV4's unbiased full-time 4WD makes it feel more like a RWD compared to Honda's very-front-biased Real Time 4WD. Driving my dad's CR-V very much like driving my old Tercel.

I thought Honda's Real Time 4WD would be better in snow, off-road conditions, etc., than Toyota's full-time 4WD (RAV4, Highlander, Sienna) because Honda's RT4WD doesn't kick in until you really need it. However, the one big disadvantage of Honda's RT4WD is that no more than 33% (or is it 30%?) of the total tourque is transferred to the rear axle at any given time, whereas Toyota's full-time 4WD system is 50/50 unbiased (at least with the 2004 with a 5-speed manual).

I've had my RAV4 since late June 2004. I have never made my wheels spin on dry pavement, even when I accelerate hard. The four wheels just dutifully drive the car. However, I do feel some slight slippage (albeit not much) with my RAV4 in the rain (which we get a lot of in Vancouver!). In the snow, my RAV4 is an absolute charm, after the rare snow storms we experienced in Vancouver earlier this month.

Luckily, I didn't buy the Element. Mind you, for the sake of versatility, the Element was a very good choice (given that I originally wanted to buy a pickup), but I went with the RAV4, due to price, availability (Elements sell like hotcakes in Vancouver) and, of course, legendary, unsurpassed Toyota quality.

Guest · Jan 16, 2005

"It seems like everybody else who makes a comparison between the RAV4 and the CR-V always picks the CR-V hands down"

I beg to differ...I've owned a 97 RAV4, a CR-V, and now a 2004 RAV4. The RAV4 with full-time AWD is vastly superior to the CR-V "real-time" 4WD system in the snow. By the time the CR-V senses front-wheel spin and sends power to the real wheels, you are stuck and not going anywhere. The RAV4 also handles much better on mountain roads. The 4.2's also caught up to the CR-V in terms of interior styling as well.

Guest · Jan 17, 2005

KCZ said:
"It seems like everybody else who makes a comparison between the RAV4 and the CR-V always picks the CR-V hands down"

I beg to differ...I've owned a 97 RAV4, a CR-V, and now a 2004 RAV4. The RAV4 with full-time AWD is vastly superior to the CR-V "real-time" 4WD system in the snow. By the time the CR-V senses front-wheel spin and sends power to the real wheels, you are stuck and not going anywhere. The RAV4 also handles much better on mountain roads. The 4.2's also caught up to the CR-V in terms of interior styling as well.

Thanks for the clarification.

The 4.2 generation of RAV4s, particularly the 2004-05 models with the 161 hp 2.4L engines, have come a L-O-N-G to be competitive with the CR-Vs (and better than the CR-V, in my opinion). Still... there are lots of people who would pick a CR-V over a RAV4 due to size of the CR-V, and the ill-conceived stereotype that Toyota is all about quality and little about performance (a stereotype that I personally do not subscribe to!). :x

When I drive my dad's 2000 CR-V, I notice a slight lag time between the front wheels slipping and the RT4WD kicking in, on both snow and gravel roads. Since the RAV4 has an unbiased 4WD system, I don't feel any slippage at all on gravel roads and very little slippage in snow because the tourque is distributed evenly among the four wheels.

Essentially, Honda vehicles with RT4WD are pretty much more FWD than 4WD because of the way RT4WD works.

However, some Toyota 4WD vehicles, such as the Matrix and some older 4WD passenger vehicles, use a 4WD system that is similar to Honda's RT4WD, in that the rear wheels do not kick in until there is any front wheel slippage.

Slayer · Jan 17, 2005

It really is a matter of personal preferences, too. On the CRV boards I've seen people talk about choosing between the Rav and CRV. Of course, they picked the CRV but their bias was really in terms of looks and function. They preferred the somewhat utilitarian looks of the V(they don't like the cute girly looks of the Rav) and the extra room vs the Rav4. Here, looks like the Rav4 owners prefered the more bold styling and awd vs the plainjane looks of the V and its RTAWD system. Room isn't so much an issue for us as it is with V owners fron what I've been observing. Oh and the Rav4 also seems to have an advantage over the V in the sand. There was a thread a few months back in the Rav4oz forums on the guys there doing some sand duning.

Guest · Jan 17, 2005

Slayer said:
It really is a matter of personal preferences, too. On the CRV boards I've seen people talk about choosing between the RAV and CRV. Of course, they picked the CRV but their bias was really in terms of looks and function. They preferred the somewhat utilitarian looks of the V(they don't like the cute girly looks of the RAV) and the extra room vs the RAV4. Here, looks like the RAV4 owners prefered the more bold styling and awd vs the plainjane looks of the V and its RTAWD system. Room isn't so much an issue for us as it is with V owners fron what I've been observing. Oh and the RAV4 also seems to have an advantage over the V in the sand. There was a thread a few months back in the Rav4oz forums on the guys there doing some sand duning.

Yes, it all comes down to preference and taste. Again, I almost went for the Element due its unique styling and functionality (64 seating/cargo area configurations!). I've always liked both Honda and Toyota, but I've always liked Toyota even more because... well, I don't know why... :lol: Fitting my bike into my RAV4 is a bit of a chore (barely fits), and I can't imagine what it would be like if I bought a new, bigger bike. I would probably have to take off the front wheel (or remove one of the rear seats), which itself is going to be a pain (and would defeat the purpose of me getting an SUV in the first place!). I don't plan on getting a new bike soon, so I shouldn't fret. :wink:

Interesting about the RAV4 vs. CR-V in sand! RT4WD isn't too bad for driving in the Vancouver rain, especially after the first rainfall after a dry spell, when roads are the most slick, as well as in light snow. However, I wouldn't trust RT4WD at all in any off-road condition (sand, etc.), or anything close so it!

4WD? AWD?

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RAVMAN

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Jeff

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Mohit

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JW

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