New to 4Runner and 4wd/VSC, help please!!!

[B4chacon]

Hi all,
I live in the mountains of SLC, UT and purchased 2006 4runner. Please do not laugh and excuse my ignorance. When would I need to turn on and lock the center differential? The 4R handles fairly well in the snow with the VSC, but there are times when we have a lot of snow and no snow blows. Any help appreciated.

 

[cabowally]

What you seek is well documented in the owner's manual.




.

 

[Keros]

I've not found a need to lock up the center diff yet driving on improved roads in the winter. I tried driving around the city for a bit with it locked, but the induced understeer on the snow and ice was... dangerous, to say the least.

I would imagine the only time you'll NEED to lock up the center diff is when you go off in the rough, need to yank someone out, or go through some real deep snow.

Locking the center diff up to deal with ice or slippery hardpack will make things worse not better.

 

[Jeff S.]

Locking the center diff up to deal with ice or slippery hardpack will make things worse not better.

Not my experience. On really icy roads my 4Runner will start to lose traction (especially when taking-off from a stop) in 4H, and I'll get lots of gizmo beeping from the dash. Once I lock the center (4HL), there is no problem taking-off, and the truck feels much more sure footed.

Our center differential is a Torsen unit. "Locking" it really is just bypassing the differential. The differential, when unlocked, allows the front and rear driveshafts to spin at different speeds. The benefit is that our 4H is a full-time 4WD. The negative consequence of an open or "unlocked" differential is that, like all differentials, it's going to transfer torque through the path of least resistance (allowing slip is the purpose of a diff). Mechanically locking a differential is the only real option to keep power moving equally during a complete loss of traction to a single tire/axel. Limited-slip (LSD) or electronic traction control systems help, but the problem in these "solutions" is that it is the job of a differential to allow slip. In other words, these "solutions" are working against the function of the diff. If two tires on the same axel (or the front and rear driveshafts) are forced to spin at the same speeds you'll either bind the drivetrain or scrub a tire. LSD's work by not allowing too much slip within the differential, while traction control systems apply brakes to spinning wheels in an attempt to send torque to the tire with traction. Thus, such systems are reactive and inconsistent. Watch a video of a Rav4 or Highlander with three tires without traction and the tires will spin all day with the vehicle just sitting there.

On really icy roads (or any surface with very low traction), if an axel loses traction it'll rob torque from the other axel. Theoretically, without any form of LSD or electronics, our 4WD system can get stuck if just one tire is spinning. However the Torsen T3 unit is supposed to be really advanced in terms of sensing and delivering torque. Their product page claims that,

"...Unlike conventional speed sensing, limited-slip differentials, TORSEN T-3 is a full-time torque-sensing, torque biasing system. Torque and differentiation are continuously managed between the front and rear axles and biased instantaneously according to variable road conditions, automatically shifting the power to the wheel with the most traction before any wheel slip can occur." Torsen T-3 Differential

No doubt it's a great unit, but I've been stuck before in 4H and the moment I locked the center... not even a hitch rolling out.


I think 4H is great for the vast majority of limited traction situations, but, personally, I've found that locking the center aids in traction especially when slopes/grades are involved. Yes, locking the center diff also turns off VSC, but that's a benefit on extremely low traction surfaces: having a computer cut the throttle when tire slippage is sensed is preposterous when road conditions guarantee a loss of traction. In my opinion, VSC is great for unexpected tire slippage or unexpected fish tailing, but if you are expecting it, then VSC becomes a hinderance.

Thus, if the roads are extremely slippery, there is no reason why locking the center diff will make matters worse. To the contrary, locking it will ensure a near-equal transfer of power between axels and will prevent the computer from cutting the throttle.

 

[Keros]

Not my experience.

Locking the center diff will force one front and one rear wheel to do the same speed. Which is fine at low speed, but as speed increases, so will the relative difference between all 4 wheels through turns. Hence, that having the center diff locked will induce understeer, as one front wheel skids under cornering load. It's not a big deal at low speed, but at +40kph, you're better off without the center diff locked.

Yes, locking the center diff will get you moving easier in any situation, or keep you moving in tough low speed situations.

But hence my specification of ice and slippery hardpack, generally you find those surfaces on highways and major roads. If you're getting moving on those surfaces, by all means the CDL is a great tool... but you'll likely want it off once you're moving at a good pace to take advantage of the center diff.

 

[B4chacon]

ok, but not helpful

What you seek is well documented in the owner's manual.

Cabowally, Of course I could look in drivers manual. But, I wanted and posted this here because I figure others have 'experience'. I find experience from others more valuable then reading in book.

 

[B4chacon]

Thanks all

Keros and Jeff S. thank you for the info, I will check it out.

 

[CAN-03runner]

Maybe if you are familiar with a typical 4x4........ With your 4runner 4hi is awd, and 4hi center lock is 4x4, like a typical 4x4 suv or pickup.

For the typical driving in snow and ice 4hi works well for me. Even in deeper snow with momentum, meaning you're already driving i can get through even deep snow. If I park in a spot, and i have a snow mound infront of the tires, or the snow plow came by and pushed snow on me, then i find 4hi is not enough. I need to lock the center. 4hi works too, but you need to give it more gas. With the center lock, i experience little to no spinning of tires, and can control getting out with barely giving gas.

The nice about being in 4hi awd and then having a center lock button for 4hi 4x4 is that it can be activated while driving, so yiu can quickly go in and out of awd and 4x4 as you think you need it.

 

[BlackWorksInc]

I believe at 40kph you'll be engaging the TRAC/ATRAC system if getting significant traction differences in each wheel. So even if the center diff is locked, the vehicle will attempt to "lock" the axles/mimic an LSD in the front and rear diffs.

 

[Jeff S.]

Locking the center diff will force one front and one rear wheel to do the same speed. Which is fine at low speed, but as speed increases, so will the relative difference between all 4 wheels through turns. Hence, that having the center diff locked will induce understeer, as one front wheel skids under cornering load. It's not a big deal at low speed, but at +40kph, you're better off without the center diff locked.

There are times when packed snow covers the road and it is a bit slick and, though everybody is driving carefully, the speed of traffic is still 35MPH or greater. In those conditions, I agree that 4H is plenty. If the speed of traffic is 35MPH, 40MPH, 45MPH and so on, then I wouldn't consider the road to be extremely slick.

However, in truly icy or extreme conditions (the type of conditions in which the roads are so slick or it's snowing so hard that everybody is driving from a crawl to under 20 MPH on major roads), I maintain that a locked differential will provide better traction. In ice-skating-rink conditions, nobody will be driving faster than 35MPH, plus the lack of friction allows tires to slip a bit, thus there will not be any driveline pressure.

Basically, if the tires cannot slip from the road conditions, then locking the differential is not the best idea, as the differential is needed to allow slip and prevent binding or pressure. However, if the tires can easily slip on the road (the slipping of the tires will do the job of the differential), then traction is more important than having a differential adjust (lose) torque.

Yes, locking the center diff will get you moving easier in any situation, or keep you moving in tough low speed situations.

Yeah, I think we're saying the same thing...

But hence my specification of ice and slippery hardpack, generally you find those surfaces on highways and major roads. If you're getting moving on those surfaces, by all means the CDL is a great tool... but you'll likely want it off once you're moving at a good pace to take advantage of the center diff.

That's a great thing about our 4WD system. It's so easy and fast to change modes. I love being able to lock/unlock the center diff on the fly.

 

[SUP3RJEFF]

Thanks for the practical info guys, this is good stuff for those of us that could use a little extra info on the proper use of the diff lock!

 

[hkollie1]

B4

We have been driving around in the same mess the past couple days, I have been enjoying it really...my 2003 4runner with old BFG's and the VSC off, has been a beast!

I lock it for all the slushy, unplowed roads that we seem to have around here especially the hills. The more tense the driving situation the more likely I will lock it.

Once I am driving on pretty clean roads, I take it off...also when maneuvering in tight spots to avoid the hopping, and binding, that can't be good.

Good Luck and enjoy!

KO

 

[earthrealm]

if i may throw in my own question, hope it doesnt sound stupid..i have 4,3, and 2L on my gear, though i normally leave it in 'D'....just want to be sure am doing the right thing

 

[BlackWorksInc]

That's fine. D is essentially telling the vehicle "I want to use all gears including OverDrive," each subsequent notch down is telling the computer "I want to use up to this set of gears."

I personally will throw my vehicle into 2 or L if I don't want the transmission to upshift a bunch, but for general purpose on-road & off-road driving D is perfectly fine.

 

[JB.]

Hi all,
I live in the mountains of SLC, UT and purchased 2006 4runner. Please do not laugh and excuse my ignorance. When would I need to turn on and lock the center differential? The 4R handles fairly well in the snow with the VSC, but there are times when we have a lot of snow and no snow blows. Any help appreciated.

The short answer is that you should almost never need to lock the center diff in on-road conditions. If you ever did need to, it would almost certainly be from a stopped position with the wheels in a ditch or depression or something. On the other hand, if you're plowing snow and going very slowly, by all means lock it.

I strongly suggest you take the time to find a safe place to test it out each way and answer this question for yourself. If you do some take off tests on a slick surface both unlocked and locked, don't be alarmed by what you may feel happening when the diff is unlocked. Don't be afraid to apply throttle but don't mash it to the floor. Ignore what you feel happening when the diff is unlocked, but pay close attention to how fast the vehicle actually gets going compared to when it's locked. Ignore the process, but take note of the outcome. You'll know far more after doing this than after reading a hundred posts.

 

[Martinjmpr]

The short answer is that you should almost never need to lock the center diff in on-road conditions. If you ever did need to, it would almost certainly be from a stopped position with the wheels in a ditch or depression or something. On the other hand, if you're plowing snow and going very slowly, by all means lock it.

I don't agree with the part in red. The whole point of owning a vehicle like the 4runner is to keep yourself from getting into that ditch in the first place.

In fact, one of the reasons I don't like vehicles with "on demand 4wd" or similar so-called AWD systems is that they don't kick in until the primary drive wheels start slipping, which IMO is too late.

This is my first winter with my 4runner and my first experience with multi-mode 4wd. With the exception of the AWD Subaru Outback I owned from 2003 - 2007, all of my 4wd vehicles have had "conventional" 4wd, meaning 4wd that you cannot use on dry, hard-surfaced roads.

So, from my viewpoint, if I'm in a sitution where, in my previous vehicle, I would have put it in 4wd high (like deep snow), then I lock the center diff. Because center diff locked = "conventional" 4wd.

But, if it's only wet or intermittently icy with patches of dry road in between the ice/snow, I leave it in unlocked 4hi.

To me, that's what makes multi-mode so great, in my previous vehicles, I'd have to either leave it in 2wd on such roads (risking loss of traction when I hit the icy patches) or leave it in 4wd and hope that there was enough slippage on the icy patches to avoid drivetrain damage (which there generally was, BTW, as I never had any drivetrain issues with this type of driving.)

We got our first really big snow a couple of weeks ago and I tried at first to keep it in 4hi-unlocked. Problem I found was that every time I turned I would get the annoying "Beep-beep" of the VSC, so I figured that since I normally drove that type of road in a locked 4wd position in my previous trucks, I might as well lock the center diff and essentially transform my truck into a regular, conventional 4wd vehicle.

I strongly suggest you take the time to find a safe place to test it out each way and answer this question for yourself.

Yup, you need to practice to figure out what works for you. Just remember that decent tires and common sense will do you better than any traction control devices. Practice will give you a good sense of what your 4runner can and can't do. So far I'm very impressed with mine.

 

[JB.]

I don't agree with the part in red. The whole point of owning a vehicle like the 4runner is to keep yourself from getting into that ditch in the first place.

How does locked 4wd keep you from getting into a ditch? That's what VSC, good tires, and common sense are for.

I covered the subject of deep snow and was only referring to on-road driving so I'm curious where it is -- other than very low speed situations -- that you would expect to find yourself needing the center locked and where having it locked would outweigh the steering and disabled VSC disadvantages.

 

[Martinjmpr]

I covered the subject of deep snow and was only referring to on-road driving so I'm curious where it is -- other than very low speed situations -- that you would expect to find yourself needing the center locked and where having it locked would outweigh the steering and disabled VSC disadvantages.

If you're in deep enough snow or slippery enough surfaces that your VSC is beeping every time you turn, then that's a signal that you need to lock the center diff and disable the VSC. That's what I did when we got our big snowstorm a few weeks ago.

As I said above, if the conditions are such that in a conventional 4wd vehicle (one without a center diff) I'd be in 4wd, then I lock the center diff. Examples would be if the road was covered with packed snow/ice with no intermittent patches of dry road, or if the road is completely covered with snow.

I guess maybe that's what you meant by "low speed situations" as you certainly wouldn't be driving fast in conditions like that (although I'll drive up to 30 - 40 mph on packed snow), but if you are waiting to lock the center diff until you are stuck, all you are likely to do is dig 4 equal sized holes with your tires. The time to lock your center diff (just like the time to switch from 2wd to 4wd) is before you get stuck.

 

[JB.]

If you're in deep enough snow or slippery enough surfaces that your VSC is beeping every time you turn, then that's a signal that you need to lock the center diff and disable the VSC.

Why? VSC operating in turns is exactly what is keeping you out of the aforementioned ditch. The only signal I detect is one that says slow down. Of all the possible cues that might point to needing to lock the center, I don't see that as being one. Certainly not by itself.

This is a nuanced discussion, though, that may not resolve well via words, so I don't want to create any impression of an argument.

In the end, the situation dictates the tactic and no one is in a better position to decide than the driver so the only real answer is familiarity with the specific truck.

I still wonder whether VSC sensitivity has remained consistent over the life of the 4th gen because my experience with it's snow behavior seems to be at odds with many of the descriptions I read. Of course, the type and condition of the tires involved is always hugely relevant and a potential source of massive variability in the handling characteristics.