Toyota 4WD systems explained

corancher

cl3inco, I looked at my '03 manual and Toyota says you can't tow any of the 4WD models with all 4 wheels on the ground. You can't tow the V8 (full-time 4WD) models with any wheels on the ground at all. For the V6 multimode models you can lift the rear wheels and tow them backwards with the front wheels on the ground (though they discourage it) but that's about it. You have to have it in H2 mode and gear shifter in neutral.

Lots of factors affect what you can do in towing, especially with vehicles that have transfer cases and torque-splitting or limited slip differentials. Proper lubrication is one of them.

In any case, I'd say the 4Runner is an impractical choice to tow behind another vehicle, unless it's entirely on a trailer.

cl3inco

To clarify further, my '87 4Runner is completely towable. With a manual transmission, and manual WARN hubs, the manual (page 160) indicates for towing with all 4 wheels on the ground you must........ 1) the ignition key must be in the "ACC" position, as the steering lock mechanism is not strong enough to hold the front wheels straight while towing, 2) The freewheeling hubs must be positioned to "FREE", 3) the transmission must be in neutral, and 4) transfer must be positioned to "H2".

However, for automatic transmission, you cannot tow faster than 30 MPH or farther then 50 miles. If the vehicle must be towed farther or faster, "disconnect the rear drive shaft at the rear differential to avoid damaging the transmission", and the transmission must be placed in Neutral.

Thus, this is how we have been towing our 87 manual tranny 4Runner behind a 40' RV for years.

My question relates to the difference between a 2004 V6 4WD "Multi-Mode" model versus a 2004 V8 4WD "Full-Time" model. It appears that neither model can be towed with all 4 wheels on the ground. Jeep has been capable of this trait for years, as their patented 4 wheel "freewheeling" system is a huge advantage for towing behind an RV (however, Jeeps have their own issues.........another subject, another day)

So, before we leap into buying a new 4Runner, I just want to know going into the purchase what my options are........1) towable with 4 wheels on the ground.......2) towable with 2 wheels on the ground via dolly...........or 3) NOT TOWABLE. I do not have access to 2004 O&M manual to review.

corancher

cl3inco, you can always stop by a dealer and glance through the manual of a 4Runner in their inventory to get the detailed story. That may be the most satisfying thing. My reading of my manual says that if you want any wheels on the ground, you will need to tow a V6 backwards, with its rear wheels up on a dolly. And it's still not a recommended thing to do. Myself, I just wouldn't do it. The 4Runner is a great vehicle on its own, but a lousy thing to tow in the way you want to do it.

alfster1

You forgot your 4th option - invest in a flatbed car trailer.

wiredup

OK this is my first post here and I did read back a few pages but I am going to ask this anyway.

I currently have a 98 TLC with the Locking rear diff option, I am looking at a 02 or newer model with the TRACS / VSC options and I want to know the pluses and minus of the 2 systems. I have been very happy with my 98, and have used the locking rear diff to get my TLC (and boat in tow) out of some sticky situations.

My questions are specific to mud and snow since I do live in the upper Midwest and am off road quite a bit. Will the new system send power to more than just 2 wheels if I am in a very slippery situation? In my 98 I can lock up the center and rear diff and get at least 3 wheels to get some power.

lcnovice

This is my first post. I went back to the beginning of this board and now know that you should never drive 03 LC with center diff. locked while on dry pavement.

However, I think I accidentally hit the locking switch with my knee and drove for maybe ten minutes like this. I was driving on residential steets (no faster than 30 to 40 mph). I realized the center diff. was locked when taking a 90 degree turn at about 20 miles per hour. I heard a thump noise once as I was turning. I didn't hear it again after completing the turn. I then realized that the center diff. was locked and immediately unlocked it. I also heard another thump when the system disengaged. My question is did I do any damage? and if so, how would I know? I am thinking I should go to the dealership and explain situation and have them check out the car for any damage. Does that seem necessary? Lastly, is it normal to hear a thump when system disengages?
Needless to say I will be more careful in the future. I appreciate any feedback on whether I should be worried about any damage or not.

Thanks.

bp3959

I wouldn't go with the VSC/TRAC system for mud unless you figure out how to shut it off. Just went playing in the mud with my 2001 Sequoia and had trouble making it to the mud until I turned off the traction control(on the Sequoia you just unplug the brake fluid level sensor, stupid of Toyota to forget the off button). The problem is that traction control will idle down the engine, and you need to rev the engine to get through mud. With the TRAC off I had no trouble getting through lots of mud with 3 open differentials. As for ice, both traction control and vehicle skid control are lifesavers(literally). In alot of ice you'll overwhelm the traction control and it'll shut itself down though.

http://img33.photobucket.com/albums/v98/bp3959/

57kevin

I took my new 4 Runner off-road and tested the downhill assist. It made much noise and seemed to be failing. Is the system sluggish while slowing the truck?

wsommariva

Once I was going uphill on a very snowy day. The car barely moved. I think it was the traction control kicking in? I turned it off and the car moved like my old cars. Am I corect here?

wwest

Ever since I bought my first Lexus, a new 92 LS, I've been puzzled at just what Trac is really about. I admit that it sometimes gives me an early warning of otherwise non-obvious slippery roadbed conditions but turning it off seems to always be the best solution to get the vehicle up and going.

corancher

wsommariva, the situation is a little complicated. I've experienced what you did when attempting to move uphill in 2WD when I didn't have sufficient traction. I'm guessing the VSC/traction control system (which is rather conservative in this vehicle) is trying to keep you from spinning the tires very much and perhaps sliding sideways. It's using the brakes and de-throttling.

I described this in some detail in a post around the turn of the year; I think it was in the main 4Runner discussion. I experimented quite a bit and think I learned some about how the system is designed to function. Perhaps that post will be of some use.

intmed99

It's too bad that i can't link my explanation on my 4runner forum of the system on this forum. Anyway, VSC and ATRAC are two separate things. When off-roading, MAKE SURE THAT YOU LOCK THE CENTER DIFFERENTIAL! Why?? When you lock the center differential, you turn OFF VSC. VSC is the part of the system that DETHROTTLES (cuts engine power) you! ATRAC does NOT!

For definition: ATRAC = 4-wheel traction control. VSC = stability control to prevent oversteer and understeer.

So, if you're gonna play in mud or snow, or want to go up a muddy hill, then i would lock the center differential. ATRAC will then manage side-to-side power transfers by pulsing the brakes to spinning wheels. Engine power is not affected. Here's a key...if you want to power thru something or up a hill, be aggressive with the gas pedal! Don't worry about all the noises and flashing lights, just gradually press down on the gas pedal. ATRAC decreases it's intervention as RPMs go up.

I see a lot of owners just giving up when they hear the noises (of ATRAC working) or too scared to use the gas pedal. Use it...but in a gradual way! Always, LOCK THE CENTER DIFFERENTIAL. If you don't then your car won't move anyway because VSC cuts engine power.

Hope this helps.

pschreck

You never actually said what Toyota you own.

wsommariva

This was on my 2004 RAV4. We also have a 2002 RAV4 and the kid has an ECHO.

hank14

We had the same problem in our 98 Avalon front wheel drive, climbing up a steep, icy dirt road to our cabin last year. With the traction control on, the front tires began to slip and the engine power was shut down once momentum was lost. Turning the traction control off allowed us to spin the tires and progress further up the hill, though still not all the way.
This was prior to having the 99 Landcruiser, which made it up fine this year in full time mode, no diffs locked.

intmed99

The Avalon's traction control system is tied in with the dethrottling function (thus, you can't make it up the hill)...UNLIKE Land Cruiser or 4runner's system where traction control is separate from VSC/dethrottling.

wwest

I have understood that the newer LCs and 4Runner's and Sequoias FULL TIME 4WD system is the same as the HL and RX, open center diff'l and moderate braking to the slipping wheel(s) to apportion torque and therefore the engine MUST be dethrottle if the idiot at the wheel decides to keep gunning it.

nedzel

in my 2003 4Runner also dethrottles. In slippery weather, I often lock the center diff (which also defeats the traction control).

intmed99

WWEST...you need to do more research! TLC, 4runners, and Sequoia have a CENTER DIFFERENTIAL. RX and Highlander does NOT! I am surprised that you do not know this...and don't insult TLC/4runner/Sequoia by saying that the RX and HL have same 4wd system!! It is much different.

TLC/4runner/Sequoia center diff is LOCKABLE. When you LOCK the center diff, you disable VSC/dethrottling fx...4-wheel traction control is ALWAYS on!

wwest

The RX and HL both have OPEN center diff'l, in early models, pre-04 for the RX, with a VC mounted ACROSS/between the two center diff'l output shafts to provide a variable, automatic, "lock".

And if you re-read my post you will see I was only talking about the LC, etc, FULL-TIME mode, and almost everyone is now using brake modulation for engine torque apportioning in full-time mode.

And just what led you to believe the RX and HL didn't have a center diff'l??

pschreck

I thought the Highlander and the RX had the "On-Demand" type of AWD. In other words, NO AWD until slippage.

Doesn't the RAV 4 have this same system?

rbleland

RAV4 is full-time AWD, at least the 2004 model is and I think all the previous were also.

pschreck

I may be mistaken, but I believe that the marketing guys at Toyota CALL it Full-Time 4WD when in reality it is on demand. I don't believe that all the wheels are being driven all the time but rather once there is slippage the system engages all wheels. But I may be mistaken.

Subaru is an example of a Full-Time AWD system.

I'm not trying to be confrontational with this statement.

rbleland

you are wrong there. As far as I know and am told by Toyota (but I will recheck in next day or so), the RAV4 system is actually full-time AWD. I have had 2 Subies also and understand your comment, Subies are full-time AWD agreed. However, even with Subies not all the AWD work the same way (eg. automatic Forester is 90/10 front until slippage occurs, standard shift Foresters are 50/50 always). I will check with local Toyota mechanic I know.

grapevinetx

In addition to RAV4, Toyota HL and Lexus RX AWD are not on-demand, but rather full time 4WD without low range gearing. Torque goes to all four wheels all the time. AWD system in RAV4, HL, RX is very similar to Subaru. Honda, OTOH, in the Pilot and CRV, uses an on-demand system in which torque goes to the front only until slippage occurs.

wwest

At the first, initial, slippage of the front wheels on the RX, prior to 04, only about 5% of the engine torque is routed to the rear. If the front slips for an extended period, a minute or so, then the VC will stiffen up and route a maximum of 25% engine torque to the rear.

The 04 RX330 uses brake modulation at the front to force engine torque to the rear. Remove the ABS pump and it always remains simply a FWD vehicle.

By that measure I would call the Rav4, Hl, RX, Sequoia, LC, etc, Full-time systems ON-DEMAND.

rbleland

Quotes from the Toyota Canada website: "Power to all wheels all the time". "...each wheel receives about 25% of engine power under normal conditions. Should a wheel begin to slip, the viscous coupling controlled center differential limits slip and channels power to the axle with traction."
Sounds like real full-time AWD a la Subaru to me. ??

blackandblue

If the dealer put a RAV4 up on a lift for me would all 4 wheels turn at the same RPM in forward and reverse?

wwest

all wheels all the time....

And 5% rear and 95% front doesn't qualify?

Put any of these on a lift and in gear and the tires will turn but at a rate determined by the front final drive ratio vs the rear, and they are different.

A more reasonable test would be to chain it to a good solid tree (damn good commercial, that!) and watch which tires actually exhibit torque application, but again, with Trac disabled.

And you might have to disable the Trac system.

pschreck

Hey, if you're right that's great. I don't doubt you. One more reason to buy a Toyota.

We have a Outback wagon and it's been great. My only gripe is that it could be wider and have about three inches more of leg room.

tlcman

I have a FZJ-80 and have worked on UZJ-100's and off roaded many toyotas. The FZJ-80 as well as the UZJ has a OPEN center diff unless it is in low or a button is engaged. On older TLC there is not 5% or 95% stuff. (on both FZJ and UZJ) This delivers power to the front and rear axle. The FZJ has solid front and rear open axles with optional electric lockers. (on a UZJ) This means that if the front right tyre slips and the drive train rotates 1/2 more of a turn that the other wheels the front left tyre will get power due to the diff in the front (I am vaugly familiar with the way that the Independent suspension and flexible axles change the set up but from experience I would say that they are a LSD limited slip) On a FZJ-80 if the front right tyre slips then all... ALL the power is routed to that spinning wheel. If the FZJ-80's were equipped with VC then the brake would be applied to that spinning wheel and there fore the power would be sent the the other tyre and it that tyre wont move it will send it to the rear. this is OPEN diff. If it was a closed center diff then power 50/50 would be supplied to the front and rear. In a slipping situation this only guarantees power to two wheels, one front one back, which is where electro lockers or ARB lockers come in. On a UZJ there is no front locker option because I believe that they are LSD's. which means that for a UZJ you can get 3 wheels power in a slipping situation with the Center locked. Yes it is true that this is a "full time four wheel drive" system but, that is said if all wheels have traction.

hank14

I'll check my repair manuals, but I believe, and according to Cliffy1, who started this topic, all 3 differentials, including the front of the 100 series, are open. Therefore, with no differentials locked, all power is routed to the tire with the least traction.

intmed99

wwest...i stand corrected...the Highlander/RX have center diffs.

On TLC100, center diff is LOCKABLE. In normal city driving, it is open. Power is routed 50/50.

Don't forget that TLC100 has ATRAC...4-wheel traction control system. This can effectively brake the wheel with the least traction to avoid all power going to it.

tlcman

yes the Braking routs power away from the slipping wheel, but this still does not replace conventional lockers. And intmed99 you are right about the lockable center diff on the TLC (all models) and yes the power with the center diff open is routed 50/50 if all wheels have traction. And im pretty sure that the TLC front axles are LSD's because i have seen them in action one wheel slips and the other wheel gets power too. The UZJ's come optional with a rear electro locker and not for the front, and since this is a TLC where talking about they would offer electro lockers for the front if they needed them.

tlcman

I talk to a mechanic today when I picked up my LC and he said the 100 series front end is a LSD (similar to powerlockers) they have a 1/4 turn off set, i was wrong about the one half. In sharp turns or higherspeed turns they stay unlocked and "ratchet" (although ive never herd it) and when power is supplied and a wheel slips a quarter of a turn they lock. (This is similar to many FWD cars). This is different in the FZJ's to the UZJ's because of the axle change.

blackandblue

FZJ-80, UZJ-100, TLC100, ??? Is it any good on the 2004 RAV4?

tlcman

first of all FZJ's and UZJ's are TLC's UZJ's are the 100's and the FJs are the 90's. If it is a full time four wheel drive vehicle than its got a similar system.

grapevinetx

Some similarities, but also some differences. None of the 3 differentials on the RAV4 AWD are lockable, either electrically or mechanically. The center differential on the RAV4 AWD is a viscous coupling.

The rear differential on RAV4 AWD may or may not be a limited slip, depending on the options on the particular vehicle. I need to check this last statement in regard to '04 RAV4. I know it's correct for '01 thru '03 RAV4 AWD, but the option of a limited slip rear diffy may have been eliminated from the RAV4 for '04.

None of this changes the fact that the RAV4 AWD is full time AWD, or full time 4WD without low range gearing, depending upon your preference of terms.

wwest

With the availability of VSC/Trac on the 01 RX300 the rear LSD option was eliminated in favor of braking use as a "virtual" LSD. If your late model Rav4 has VSC then possibly, like the RX, the LSD was not available.

I know that like the RX, the VC was eliminated in the HL in favor of Trac brake modulation, but does anyone know if the same thing was done with the Rav4?

blackandblue

Now that the RAV4 comes standard with Traction control and ABS is the AWD that much an advantage over just front wheel drive? Worth the extra cost and maintenance?

wwest

The single biggest advantage I can think of is being able to safely use snowchains. With AWD you can add wheel spacers such that snowchains can be used ONLY on the rear.

Assuming your Rav4 shares the HL/RX AWD system and rear suspension clearance restrictions.

rbleland

If you live in snow country I would say the AWD is definitely worth it. I don't think the added maintenance costs are that high. I would only get the FWD if I lived in Cal. or Florida, etc. and never went to ski areas.

grapevinetx

I checked on the specifics on '04 RAV4 AWD. The option of having a limited slip rear differential (LSD) was eliminated and vehicle skid control (VSC) was made standard for '04. On '03 and earlier, LSD and VSC were both options and were mutually exclusive (couldn't put both on the same vehicle).

qualitynut

My research tells me that there are many different technologies available for LSD. Anyone know what technology is used (and who manufactures for them) by Toyota on the Cruiser? I have read about gears, clutches, etc.

tlcman

TLC's rear and center diffs are not stock or optionable in LSD form. Rear is optional and center is standard electronic full locking diffs. Are you talking about the front end?

hank14

According to the manual on my '99 100 series, the front differential is open, without any clutches or LSD mechanisms. The center differential is open but lockable (like all Landcruisers 80-100 series). The rear differential is open with a selectable electronic locker.

The manual does show that Landcruisers without the rear electronic locker do come with the clutch-type LSD, which can and will wear out without any indication, as Cliffy1 talked about at the beginning of this thread.

I would think the newer 100 series (2000 and up) would not need LSD's or lockers because of the traction control systems, although this could limit off road capability.

qualitynut

Thanks for the reply tlcman and hank14. I would have bet money that the manufacturer's window sticker indicated rear LSD. Checked after your replies and there is no mention of it. I agree that it shouldn't need it with the electronic systems and such.

Awesome vehicle. Full-time 4wd definately better than my old 98 JGC w/Quadra-tracII (at least on snow). Unfortunatly, wife's (family) car and I rarely get to drive it.

tlcman

although the TLC's have the trac braking system this does not replace conventional lockers. Yes for the non off road enthusiast lockers are not needed, and the braking system will work fine. But for the regular off roader lockers will still be a necessity. The Braking system will rerout some but not all of the power away from the slipping wheel. I highly doubt that lockers will be completely replaced by the braking systems.

wwest

In many instances the front and rear "lockers" have already gone away in favor of the use of the brakes to simulate LSDs.

tlcman

If you read my last post... I said that they are great for the non off road enthusiast but. they DO NOT replace lockers. lockers give equal power to each wheel... brakes take power away from a slipping wheel and give it to the others, guess what for an off road enthusiast you will eat up your brakes very quickly if you do not have lockable diffs let alone you will not be able to cross mud in the same fashion as you would if you had lockers.
Rear lockers are still offered in TLC's and they are still available for most any kind of trucks. Not many trucks come with the option of lockers....ever...thats a fact, TLC's are one of the few SUV's that are available with stock lockers even back in 94' when I got mine and there was no such thing as trac. Braking systems will not replace lockers as long as I off road....(well until I can get my TLC fixed after my sister who was staying with me for a while rolled it over)