locked or unlocked when pavement ends?

[cmoney]

Hey everyone, i'm relatively new to this forum as i just purchased my 4runner last October. Since then, I've taken it out about 4 - 5 times (mojave road, anza borrego, big bear, and lone pine area).

So far this is what i've been doing. As soon as pavement ends, but on a decently maintained dirt or gravel road, i put it in 4hi unlocked. I pretty much keep it in this mode unless i climb a steep hill, hit soft sand, or expect mud.

i've gotten stuck a few times, once in sand and once in mud, and i would switch to 4lo unlocked, and if that doesn't get me out, i would lock it in 4lo. Luckily that has gotten me moving after some major revving and once i get some momentum i eventually got out.

Is this what everyone else is doing? Or do you guys lock it in 4hi much earlier? The only reason i'm hesitant to lock earlier is because I want to compromise handling and be able to take sharper turns.

I've read somewhere that unlock mode is actually better on snow, but lock is definitely better for mud and sand.

Any thoughts and feedback on ths topic would be greatly appreciated!

 

[KidVermicious]

You've got it. As you get more experience, you'll get a better idea of when you'll be needing to lock up before you get stuck.

I recommend doing everything possible to get out without the locker first, though. If you learn to read the trail and pick a correct line in the first place, you won't need that locker near as much as you think you do. Don't let it be a crutch.

Deep snow is a lot like mud, locking can help you keep momentum. Don't lock up on snowy/icy roads though, that's definitely counter-productive.

Wheel safe!

 

[Hyde802]

Now before we get to much farther into this conversation..are you talking about a selectable differential locker, or maunal hubs...

 

[KidVermicious]

Now before we get to much farther into this conversation..are you talking about a selectable differential locker, or maunal hubs...

If he's waiting to lock his hubs until he's in 4lo, there's a bigger problem....

 

[Hyde802]

Thats why Im asking...Haha. :lookout:

Edit: I think he has a 4th gen. Never mind, Haha.

Well then back on topic....I go into 4low when I start going under 20mph. And I have a spool, so locked always.

 

[BucknutBob]

In stuff like sand and mud, you want to stay in 4-HI, not 4-Low--the higher gearing will help you to stay on top of the soft stuff. Using low-range will just make you dig in too much. Lower your tire pressure, use high-range, and maintain momentum. If you have a manual tranny, go even further to raise your gearing by selecting second gear just before entering the slop--this will keep you from digging, and will keep you from having to shift while in the goo (a definite momentum-killer). Have fun out there!

 

[cmoney]

Hey guys, thanks for the replies. I have a 4th gen do I was referring to center diff locker.

 

[KidVermicious]

Oh, center diff, I thought you were talking about a rear locker. I don't have a lot of experience with those - my understanding is that you have a differential in your transfer case that gives you all-time 4wd? In that case, I would engage that center diff lock any time you're on dirt. When it's engaged, it acts just like the part-time 4wd in my 1st gen, and doesn't allow the drivelines to turn at different speeds. When it isn't, they can slip and you could conceivably lose power if just one wheel breaks traction.

I think that's how that center diff works anyway. Hopefully another 4th gen owner can wander by and set us straight.

 

[JB.]

You might want to edit your first post to state up front you have a 4th gen.

As soon as pavement ends, but on a decently maintained dirt or gravel road, i put it in 4hi unlocked. I pretty much keep it in this mode unless i climb a steep hill, hit soft sand, or expect mud.

It's preference. In that mode if it's a pretty fast, graded dirt road you'll have VSC available if you cook a corner too fast. On the other hand, I often prefer the predictable understeer of being center locked on a road like that. I go back and forth, but that's the beauty of having center diff lock nearly instantly available at the push of a button at any speed.

When to go to low range is much more straight forward but, even there, I'm on and off the CDL button a lot. Sure, a tight turn on dirt is less stressful than on pavement so many might say just leave it on, but if you have the quick unlock option, why make that turn with the center locked? It may be less stressful than pavement, but there is still much more stress than unlocked. Because of that, and the fact that VSC is out of the picture in low range making the truck very capable even with CDL off, I tend to run with it off there too, knowing that it's almost instantly available. If you ever have to make a real tight turn on slickrock, you'll really learn to appreciate that option.

I've read somewhere that unlock mode is actually better on snow, but lock is definitely better for mud and sand.

You may be thinking of mixed conditions on pavement where full-time 4WD can be used without limit.

 

[CAN-03runner]

In a 4th Gen if you manage to get the Atrac to engage, and you keep on it, it works wonders. It always amazes me.

With the center diff the front and rear can differentiate. So power is constantly shifted front to rear, rear to front. With the center locked it is 50/50 front rear.

Theory goes like this is I understand it right and can explain it. You're going up a steep hill, in 4x4 you're almost over the crest and you just can't make it any more, the truck feels like it is bogged down, it finally stops going. Too much weight on the rear, tires digging in, and not enough weight on the front and the rear just can't turn those wheels anymore. And since the center is locked, if the rear is blocked up, the front can't do much either.

You do it again with the center diff unlocked but now the center diff can transfer power. Similar scenario but this time the center diff being unlocked can transfer up to 70% of the power to rear, it could be enough to get those rear wheels to keep turning and get you over.

The best thing you can do though is, bring a friend, with a truck, and a recovery strap. Then you can try the different sceanrios using different combinations of 4lo, 4hi, locked not locked etc... and be pulled out if it's a no go.

 

[JB.]

You do it again with the center diff unlocked but now the center diff can transfer power. Similar scenario but this time the center diff being unlocked can transfer up to 70% of the power to rear, it could be enough to get those rear wheels to keep turning and get you over.

You're right about the transfer of torque with the Torsen diff. It makes CDL off a quite capable mode, but a locked center can transfer up to 100% of the available torque to one end (if it can support it).

 

[cmoney]

JB i'm with on this one. i'm thinking why put unnecessary stress on turns when we have the option of keeping it unlocked. i think so far i havent tackled any moderate to technical trails yet so i didn't need to lock, besides those two occasions when i almost got stuck. i think this will change as i go on more difficult trails once summer comes around.

JB, do you any rock crawling? im wondering in that terrain is it better to lock or unlock. I thinking 4lo would be ideal as it will allow you to control speed better. Lock would give you better traction if one wheel slips but i can see the need to make sharp turns to take a certain line as well so unlock would be better. Then again, most trucks are part-time and they manage to negotiate sharp turns well enough.

 

[BucknutBob]

4-LO is definitely the choice for rocks, cmoney--low speed, good traction, lower gearing for powering over objects with small throttle adjustments. The lower the gearing, the better when it comes to crawling--this is why you see guys with double T-cases, to further multiply their overall ratios for power right off idle. As for the center diff, you should be fine keeping it locked so you can concentrate on the trail--as you said, part-time rigs do it all the time. The locker that will make a big difference for tight turns is a selectable locker in the front diff--keeping those locked on tight turns puts a lot of stress on the drivetrain, so guys will switch them off briefly, then right back on once they straighten out. Mind you, this is for bends in the trail, not for individual obstacles where the wheels are turned for better angles--you want fully-locked until you're clear, to keep from spinning over rocks or trees, etc.

 

[CAN-03runner]

4Lo center diff locked is also beneficial going down hill offroad.

 

[JB.]

JB i'm with on this one. i'm thinking why put unnecessary stress on turns when we have the option of keeping it unlocked. i think so far i havent tackled any moderate to technical trails yet so i didn't need to lock, besides those two occasions when i almost got stuck. i think this will change as i go on more difficult trails once summer comes around.

JB, do you any rock crawling? im wondering in that terrain is it better to lock or unlock. I thinking 4lo would be ideal as it will allow you to control speed better. Lock would give you better traction if one wheel slips but i can see the need to make sharp turns to take a certain line as well so unlock would be better. Then again, most trucks are part-time and they manage to negotiate sharp turns well enough.

If there's any doubt about the terrain, I don't hesitate to use CDL ON. When in doubt (rocky, muddy, snowy or steep - downhill or up) it should be locked, but having the unlocked option is nice, and I think has more uses than people who haven't experienced it might suspect.

Another example that comes to mind. Say a twisty, gravely, sandy wash that allows enough speed to be fun while requiring the dodging of rocks and bushes. The vehicle tracks better with CDL OFF allowing for better avoidance and a little more speed. Someone who didn't have the option would never miss it, but when it's there, and you can instantly compare the two driving states, it's easy to appreciate. It's the pleasant feel of the easy and precise steering that induces me to run CDL OFF more than might sound reasonable to someone used to traditional 4wd.

 

[cmoney]

Bucknutbob - thanks for the insights. it makes sense that even turning the steering wheel at half to full lock while rockcrawling is merely tire placement, not much travel is going on so binding isn't an issue. didn't realize that until you brought it up.

JB - yeah i did some of that at anza borrego down in san diego. plenty of wide open washes out there for higher speed runs. like you said, the only steering to be done is avoiding bushes and bigger rocks. from my experience vsc kicked in every couple of minutes. the braking didn't annoy me as much as the beeping sound! i knew i coulda turned vsc off but just wanted to be a little safer.

 

[JB.]

JB - yeah i did some of that at anza borrego down in san diego. plenty of wide open washes out there for higher speed runs. like you said, the only steering to be done is avoiding bushes and bigger rocks. from my experience vsc kicked in every couple of minutes. the braking didn't annoy me as much as the beeping sound! i knew i coulda turned vsc off but just wanted to be a little safer.

Yeah, in high range VSC can be an irritant occasionally. If you have a 2008 or 9 there's a dedicated button to turn it off without locking the diff. There's a VSC off mod that can be done, or you can pull a plug from under the hood to temporarily disable all ABS functions. I've never found the need to do either. Often the conditions are such that 4th gear-low gives me all the speed I need so VSC is out of the picture.

Running hard in something like sand for lengthy periods has the potential to heat up the trans fluid from the torque converter running mostly unlocked. The TC will lock in 4th gear (no 5th in low) so if 4th low gives me enough speed (don't like to push it much past 25mph) and the conditions warrant, I try to use it.

 

[ajordan1975]

welded!

 

[crackiswack]

You're right about the transfer of torque with the Torsen diff. It makes CDL off a quite capable mode, but a locked center can transfer up to 100% of the available torque to one end (if it can support it).

Can you explain this one further? This is not my understanding of a standard locked 4wd system, power is 50/50 F/R, how does the the locked Torsen allow 100% of the power to go to one end?

 

[crackiswack]

You do it again with the center diff unlocked but now the center diff can transfer power. Similar scenario but this time the center diff being unlocked can transfer up to 70% of the power to rear, it could be enough to get those rear wheels to keep turning and get you over.

Are you assuming the ATRAC would brake the front wheels to allow torque to transfer to the rear? Have you confirmed this actually happens and is benefitial, ie the transfer of the power to the rear wheels overcomes the additional drag on the front wheels from the brakes being applied?
Edit: N/M the Torsen continues to work as long as there is some traction, it only completely fails when a set of wheels loses complete traction