Center diff lock question on V8 4Runner

[kafene]

Spent a big chunk trying to understand all the different kinds of traction stuff and I still don't feel like I "totally get it". Please don't try to explain it... it's just too damn confusing. Every time I feel like I understand, I read something else that throws it off. BUT.... I do have a question.

I have a 2004 V8, so it's full time 4WD. To me, that means I have power going to 2 wheels, one in front and one in back. In this setup, if I get stuck, I take it that the power goes to the wheel w/ the least resistance. I'm guessing this is the same for both the front and rear axles. I'm bringing this up because there have been a couple of times where I felt like I really could use a locked axle (front or rear), and I've been told I have open diffs., which I concur.

My question is... what the hell is the Center Diff Lock button for? Also, does the center diff lock react any different if I'm in 4Lo or 4Hi? ....because when I used the Center Lock, it sure didn't seem like it helped me get out (but then maybe it did since I didn't try it with the center diff lock off). :headscratch:

If it's going to take a big ole' explanation, than never mind. It already bothers me that I have to ask this question having had my truck for almost three years. :shake: :loser:

[troyboy162]

my understanding is you have power going to the the one of the 4 tires with the least amount of traction, because the transfer case is a "open diff" between the front and rear. This is why you can be in 4wheel drive on pavment where I cant.

locking the transfer case gives you a true 50/50 split of power to the front and rear. now you will have one tire on each end with power.

How it behaves in 4hi vs 4low...I have no idea. as long as you dont lock it on the street then you should be fine to experiment.

[04 Rocko Taco]

my understanding is you have power going to the the one of the 4 tires with the least amount of traction, because the transfer case is a "open diff" between the front and rear. This is why you can be in 4wheel drive on pavment where I cant.

locking the transfer case gives you a true 50/50 split of power to the front and rear. now you will have one tire on each end with power.

How it behaves in 4hi vs 4low...I have no idea. as long as you dont lock it on the street then you should be fine to experiment.




This is my understanding as well. (we have a 96 FJ80 with center diff lock, but we also have the good fortune to have front and rear lockers as well)

[kafene]

locking the transfer case gives you a true 50/50 split of power to the front and rear. now you will have one tire on each end with power.


That's what kind of confuses me. If locking my center diff gives me 50/50 between the front and rear, what is it when it's not locked since my V8 is full-time 4WD?

I guess maybe that's what I'm confused about. What is the "normal" 4WD in the V8 4Runner? I guess I feel like full-time 4WD should mean it already has 50/50 and that center lock SHOULD be what an axle lock should do. Obviously this is not the case.

[YotaFun]

my understanding is you have power going to the the one of the 4 tires with the least amount of traction, because the transfer case is a "open diff" between the front and rear. This is why you can be in 4wheel drive on pavment where I cant.

locking the transfer case gives you a true 50/50 split of power to the front and rear. now you will have one tire on each end with power.

How it behaves in 4hi vs 4low...I have no idea. as long as you dont lock it on the street then you should be fine to experiment.


He hit the nail on the head

When its not locked it like having an open diff, on an axle, the two tires get the power but the minute one tire looses traction it will get more power, so in this case lets say the rear tires loose traction but the front still has good traction, the power will go to the rear and spin the rear tires more

[Seanz0rz]

OK, let me do my best here

Every day, your 4runner is a type of all wheel drive. what this means is on dry roads, power is going to all 4 wheels, but each diff (front, rear, and center) is equalizing the loads from each wheel and each axle, resulting in normal performance. if for any reason one wheel spins, all power will be transferred to that wheel, resulting in a loss of traction and forward (or reverse) progress.

when you engage the center diff lock, you are turning your AWD system into a traditional 4 wheel drive system, like the one i have in my 4runner. this center diff lock locks out the center diff, effectively linking the front and rear drive shafts together. if you lose traction on the front axle, all the power going to the front axle will go to the wheel with no traction, BUT, the rear axle will still get the same amount of power.

similarly, with a locked rear axle for example, power will go to the wheel with least traction, but with a axle diff lock, power will be split equally between the wheels.


I think this should help you understand how it works: http://auto.howstuffworks.com/differential.htm

Now, that being said, here is what you REALLY need to know
Street: High range and center diff unlocked
Dirt road: high range and center diff locked
rocks: low range and center diff locked.

basically toyota added the center diff to allow it to be all wheel drive for the street. they added the locker to still be capable offroad.

[DHC6twinotter]

Doesn't the 4Runner use a Torsen center diff? How different is a Torsen diff when compared to an open diff?

My understanding is that a Torsen center diff will always send power to the both axles, but with varying amount front to back depending on traction. With an open diff, the power goes to the wheel with the least amount of traction, but with a Torsen, some of that power still goes to the wheel with traction, even if the diff is unlocked. Locking the diff will send the power 50/50 front/back.

Somebody correct me if I'm wrong.

[kafene]

OK, let me do my best here

Every day, your 4runner is a type of all wheel drive. what this means is on dry roads, power is going to all 4 wheels, but each diff (front, rear, and center) is equalizing the loads from each wheel and each axle, resulting in normal performance. if for any reason one wheel spins, all power will be transferred to that wheel, resulting in a loss of traction and forward (or reverse) progress.

when you engage the center diff lock, you are turning your AWD system into a traditional 4 wheel drive system, like the one i have in my 4runner. this center diff lock locks out the center diff, effectively linking the front and rear drive shafts together. if you lose traction on the front axle, all the power going to the front axle will go to the wheel with no traction, BUT, the rear axle will still get the same amount of power.

similarly, with a locked rear axle for example, power will go to the wheel with least traction, but with a axle diff lock, power will be split equally between the wheels.


I think this should help you understand how it works: http://auto.howstuffworks.com/differential.htm

Now, that being said, here is what you REALLY need to know
Street: High range and center diff unlocked
Dirt road: high range and center diff locked
rocks: low range and center diff locked.

basically toyota added the center diff to allow it to be all wheel drive for the street. they added the locker to still be capable offroad.


Thanks for the link, Sean....I think I finally get it... damn! Part of the reason I was so confused is because I was thinking the "traditional 4WD" is what I thought it had already without the center diff lock engaged. The reason being, if I'm on a DRY surface with good traction, I DON'T CARE if I'm 4WD, because I'm moving. I'm not stuck, so 4 wheel, 3 wheel, 1 wheel.... I'm not stuck, why does it even matter to me? It's when I'm STUCK that I need help, and losing traction on a wheel in the front and one in the back means I'm basically not going anywhere since both sides have a wheel w/ no traction (least resistance).

Now, I will say it DOES help in dirt conditions (since the "weak" wheel still has measurable traction), but I feel like I'd rather forgo the center diff lock and have a REAL lock instead. :(

Hey Daniel, Sean's link explains the Torsen (TORque SENsing) differential pretty good. You're kinda on the right track, but as Sean said, if one of the front or rear tire is spinning, it splits the power front and back. The problem is if there's one spin in the front and one spin in the back that causes us to get stuck. This can happen in snow, mud, and really soft sand.

Basically, I need to get a real locker, unless I'm only going to stay on dry, TRACTION surfaces... and that's not always easy to predict when you go exploring.

[Seanz0rz]

I went alot of places with unlocked axles. I still do. when you lock your center diff, you are like my truck in 4wd. very capable! alot of that capability though is skill and more importantly practice. Come with us up to big bear next time and we will put you through your paces.

even better, come up to hungry valley for the toys for tots toy drive and we can play on the practice ramp!

[Good Times]

the center diff locks basically forces the power to be distributed 50% to the front and 50% to the back. now this doesn't mean you're getting 25% to the front right, 25% to the front left, 25% to the rear right and 25% to the rear left. to get 25% on all four corners you need a front and rear locker. which ensures that you're getting 25% on each tire.

the awd system we have is really a complex work of art using the "well sort of the latest" technology out there. (obviously this is at the time of production). it basically utilizes a system of checks and balances with the way you drive and the road condition to determine the best power balance to distribute the power down to the wheels. This means that the power may be 30%/70% (front/rear) or even the opposite of 70% front and 30% rear. It's calculating every chance it can and distributing the power accordingly so you the driver gets the best performance out of the vehicle.

for practical applications I just lock my center once I'm on dirt. That way I know it's 50/50 and then from there I decide if I need to lock anything else beyond that.

[kafene]

Sean, sounds good. I'll have to see about the Toy's event. I don't have my last two chemo schedules yet... and I had great news last week. Doctor said my cancer is in remission. Still need to finish the crappy chemo treatments, but still. Good news!

Lance, you have lockers right? Are either of you guys familiar on the cost of putting something like ARB lockers put in the front and rear? I also seem to remember reading somewhere that it's not that good to have lockers for the fronts of IFS trucks for some reason. I'm assuming IFS means Independent Front Suspension? Correct me if I'm wrong because I've been doing a lot of assuming lately. :)

[4x4mike]

Congratulations on the news of remission.

Installs of ARB's front and rear are pretty expensive.

[Seanz0rz]

Lockers and gears usually run about 1000 in parts, another couple hundred in labor. these are general values. if you dont want to regear, you still need a locker, install kit, and a compressor. not cheap!

Lockers are not as recommended for the front of IFS vehicles because it can put a tremendous strain on the front axles, causing them to break.

a rear locker is a good idea, but i think if i were you i would wait a while until you need one. If you are going with other people (which you should be) the need lessons if someone can tug you through a rough spot or help you stack rocks.

i think it's worth learning the limits of your vehicle without a locker before spending money on one. you may find that it just isn't necessary. instead of a front locker, i have a winch. it has been far more useful than a front locker. the couple of times where a front locker might have worked, a winch did the trick.

i would recommend a rear locker, but only after you get that thing on some dirt!

[Crinale]

These guys have it all right. For lockers like what Sean said, the ARB will be about 1000-1200 per axle plus (at minimum) a compressor (nother couple hundred) and if you want, an air tank so your compressor doesn't have to run as often.

Honestly you would probably be pretty well off with a limited slip like a Detroit TruTrac (has a 3x power split, so that the wheel with more traction will get 3x the power of the wheel that is slipping. If the wheel is completely in the air it will still get all the power because 3 times zero is still zero to the other wheel. But with creative use of brakes this can be worked around)

Detroit TruTrac is like $550 per axle in parts, then the labor to install them.

[troyboy162]

Don't spend all that money to get limited slip but that's a whole other conversation

[Robinhood4x4]

Looks like everybody covered everything pretty well. The only thing I'd add is get out there and get some experience with your truck before spending the bucks on lockers. Try out the traction control (TRAC, or is it A-TRAC?) and see if it works well enough for the trails you want to run.

[troyboy162]

JD's traction control was pretty impressive on his 2004. Even when hanging a tire it would apply the right brake to keep him going. I thought it was a gimik but its pretty effective.

[kafene]

I just have the Center Lock button. Mine did not come w/ the ATRAC. Wonder if applying the ebrake manually or front brakes would help at all... I'll have to try it, unless someone's already tried and experienced any improvement at all? I know it'll apply pressure to both sides, but maybe it's enough to get the stuck wheel moving. :)

[Good Times]

Mark, your 4runner comes w/ atrac. all of em does now and it's by far a great system that works wonders. in my humble opinion I've really only needed to use my locker a few times (in scenarios where I put myself there so I knew I needed to use it). But for most practical applications I'd say the atrac system is robust enough to get you through some rough stuff.

:)

[kafene]

Thanks Lance.... right when I was getting the hang of all this traction stuff, now I gotta look up ATRAC. :thumbup:

Never bothered to read ATRAC posts since I figured didn't apply to me. You sure about the ATRAC thing? I was under the impression it was an option. :headscratch:

[Robinhood4x4]

Yes, all 4th gens have it. At least all 4wd, not sure about 2wd.

[kafene]

Yes, all 4th gens have it. At least all 4wd, not sure about 2wd.


Sweet! LOL. I'm learning so much about my 4Runner! Hahahaha!! I've been reading and watching YouTube vids on Toyota's ATRAC. Had no idea...I'm impressed. Can't wait to try it out. I've heard the noises at times when I'm wheeling, but as soon as the sound comes, I stop, then punch the accelerator to try and get myself out because I thought my truck was trying to tell me it's dying. :shake: Didn't know it was SUPPOSED to do that. I've been doing everything the opposite.

[kafene]

Quick question. Is ATRAC always on or only when I lock the center diffs?

[Jaydee914]

I believe ATRAC is always on, but it's more of a low-speed helper. And the way to use it is to be gentle on the gas, and then when you hear the noise, as long as you have the proper throttle position, just let the ATRAC sense the slippage and go to work. It usually takes a second of the truck going nowhere and then just magically start progressing again. It's definitely gotten me through some tough situations and it only gets better as I get the feel for it. A lead foot is NOT the way to get ATRAC working for you!

That being said, a rear locker is probably my next purchase. A less expensive way to go is to find an electronic locking differential from an FJ and modding our axle to take it. Look around on tr4.com and the 120 forum and you'll find a couple of these e-locker mods. I believe this winds up being about half to 75% of the cost of an ARB. The only downside is that they're not quite as strong as an air locker. This is the route I'd like to go.

Anybody want to lend a hand on an e-locker install? I'll buy the beer!

[Seanz0rz]

JD, I might be up for that. I did mine like 5 years ago.

[kafene]

Thanks for the info, JD! Hmmm... I'll have to look at the FJ locker option instead. Sounds interesting. :)

Sean, what's lifelike?

[Jaydee914]

Nice, thanks Sean! I just need to find an FJ third now...
On a related note, I really need to get out wheeling more often!

[Seanz0rz]

lifelike = stupid auto correct on my phone! i did mine like 5 years ago. it's a giant nightmare and sucks in every way possible. i'd still be up for it though, but only once i get my welder wired up and drill press set up.

[kafene]

lifelike = stupid auto correct on my phone! i did mine like 5 years ago. it's a giant nightmare and sucks in every way possible. i'd still be up for it though, but only once i get my welder wired up and drill press set up.


Hahahaha... You actually made me Google "lifelike" after I read your post! hahahaha. Whenever you guys are actually gonna do it, let me know. I'd like to stop by and hang out with you guys if I have the day off and see how it's done.

[Crinale]

Nice, thanks Sean! I just need to find an FJ third now...
On a related note, I really need to get out wheeling more often!


Is the diff any different than the older taco and 4runner elockers? It would probably be easier to find an older one. I'm just not sure if the they used the same 8" rear diff or not

[Robinhood4x4]

i did mine like 5 years ago. it's a giant nightmare and sucks in every way possible. i'd still be up for it though, but only once i get my welder wired up and drill press set up.


You're doing it wrong! :tongueout:

[Robinhood4x4]

Nice, thanks Sean! I just need to find an FJ third now...
On a related note, I really need to get out wheeling more often!


Is the diff any different than the older taco and 4runner elockers? It would probably be easier to find an older one. I'm just not sure if the they used the same 8" rear diff or not


Yeah, I don't think they're the same.

[troyboy162]

looks like the FJ and 4th gens have the same axle
http://www.toyota120.com/forum/showthread.php?t=22213

[Crinale]

That part I figured, just not sure if it was the same diff as the 3rd gen and 1st gen taco trd..

[Jaydee914]

That part I figured, just not sure if it was the same diff as the 3rd gen and 1st gen taco trd..


Yes, I believe it's they're all the same. An elocker from a 3rd gen 4Runner or FJ should just drop right into the 4th gen axle (with a little bit of modification).

[Robinhood4x4]

I'm not convinced that they're the same, but maybe they are. However, one reason to look for an FJC or newer tacoma elocker is to get the correct gear ratio.

[Jaydee914]

Turns out that ALL '96+ 4Runners (and FJC's) have the same 8" rear diff (although possibly different ratios b/w 3rd and 4th gens). Here's a good bit of info: http://home.4x4wire.com/erik/diffs/
Tacomas are not the same, it turns out. They're similar to the Tundra, instead.

[Crinale]

the trd tacomas with elocker have the same 8" diff... it is closely related to the old v6/turbo diff of the 1st/2nd gen 4runners. The non locker tacoma has a completely unrelated 8" diff that has a beefier casing and pinion bearing I believe

[Jaydee914]

Ok, after further research, here's what I've come up with for ratios:
4th gen Runner: 3.727 (3.73)
FJC: 3.90
3rd gen Runner: 4.10

So we'd need to figure out new gearing either way. Maybe an air locker would be the best option after all?

The research continues...

[troyboy162]

You need to transfer your gears to the elocker carrier I would think, but I dont know if they mate up or not. Hafta google what people are doing to make it work. re-installing the gears will take a gear install set of bearings and a set up fee. Pulling the third is at least easy.

[Jaydee914]

Here's some e-locker retrofits:

3rd gen into 4th:
http://www.toyota120.com/forum/showthread.php?t=20784
FJC'S into 4th:
http://www.toyota120.com/forum/showthread.php?t=22213

The first thread makes no mention of ratios. The second says that the FJ 3rd already came with a 3.73 ratio. Interesting.

[Robinhood4x4]

Well that's good to know. I didn't realize 4x4wire is still updating that ancient article. The gear ratio thing would be nice to sort out since paying for a gear install would at least partially negate the cost of an ARB.

[Jaydee914]

Another cost to take into account is install. I read up on an ARB install and it looks waaaaay more complicated than the elocker! Elocker seems like it can be done in a driveway with a grinder and a good drill - modify the housing, drop the donor 3rd in, and you're essentially done (ok, I simplified that, but you get the idea). The ARB involves disassembling and modifying the differential itself and then doing a precision reassembly. That's something that would have to be brought to a differential shop for a few hundred dollar install.
As far as the wiring for the elocker, there's a couple of guys out there offering custom plug and play harnesses for about $150, which makes things really easy.
All that being said now, I'm torn.

ARB:
Negatives: more expensive and needs additional compressor and labor, can't be done in a driveway.
Positives: stronger, faster engagement

elocker:
Negatives: need to regear either the truck or the donor differential? It's ability to handle 35" tires has been questioned.
Positives: Overall cost? Relative ease of install.

[YotaFun]

I know this is so hi-jacked now, but it is confirmed, if I were to take the diff from my 3rd gen and put it into a 4th gen axle it will work (with the obvious modifications)?

If so thats awesome!
My stray me towards a 4th gen in the future if something were to ever happen to the 3rd gen

[Robinhood4x4]

Well, you also need a welder in addition to the grinder and drill.

For the ARB install, you can save some money by removing the third and dropping it off at a diff shop and having them install the ARB with the air line fitting. Then, all you do is bolt up the third to the axle housing and plumb in the the compressor and air lines.

Do the electrical harness yourself. It's pretty easy and can be pieced together for $15-25 (+ cost of toyota harness), depending on how fancy you go. There are good writeups on the web, including 4x4wire. Perhaps Ken will respond with his knowledge as he's one of the original pioneers.

Another con for the ARB is the pneumatics complexity. People always say they work fine as long as the copper tube is installed correctly, but never the less, leaks are a common problem. Having said that, mine has been fine.

I think you'll need to make some calls and find out the cost of an ARB installation and add everything up for both the ARB and the elocker. That'll make your decision for you. As long as you don't have to regear, I think the elocker is going to come out ahead.

Personally, I've never had a problem with either my elocker or ARB.

[04 Rocko Taco]

I've seen elockers in 1st gen 4runners and pickups handle 37 - 40" tires, I wouldnt have any doubt at all about running an elocker on 35's.

[Robinhood4x4]

I was going to say the same thing, but the difference is this isn't a 22re anymore. It seems like most of the V8 swapped guys usually end up going with a dana 60 eventually.

I think it depends on one's driving style. If you're a pedal to the metal type of guy, then you're going to be more likely to blow it up. If you're a finesse driver, then it's probably ok.

[Jaydee914]

I think it depends on one's driving style. If you're a pedal to the metal type of guy, then you're going to be more likely to blow it up. If you're a finesse driver, then it's probably ok.

You're probably right. I'm sure the ARB is a stronger unit, but I bet the stories you hear are people beating on their trucks and blaming the e-locker when things explode.

[04 Rocko Taco]

I've got a welded rear in my '84 and a lockright in the front. If the lockright ever goes, I'll weld the front and leave a hub unlocked all the time, until I really need it.

But its a trailer queen, and wouldn't work on a DD. Although (at least on an older truck) I do not find the welded rear a problem on the street at all, except for the occasional (okay - all the time) tire squeal when turning.

[Crinale]

I think it depends on one's driving style. If you're a pedal to the metal type of guy, then you're going to be more likely to blow it up. If you're a finesse driver, then it's probably ok.

You're probably right. I'm sure the ARB is a stronger unit, but I bet the stories you hear are people beating on their trucks and blaming the e-locker when things explode.
I always take negative reviews like that with a grain of salt.. I would bet that most of the people who blow up toyota diffs are either trying to put way too much power to the ground, or just goin crazy places that'll break anything

[Jaydee914]

A related (dumb?) question; if I regear, I'd need to switch out both front and rear diffs?

[Seanz0rz]

yes, the gear ratios need to match

[Crinale]

I'm not sure how the toyota center diff works (how much of a power disparity it can handle front to rear), but you may be able to get away with doing one at a time, just never lock the center until they are the same.

[troyboy162]

if you had to...you could do the front one week and just take out the front driveshaft until you do the rear.

[Crinale]

if you had to...you could do the front one week and just take out the front driveshaft until you do the rear.
In that case, you would have to run the center diff lock, or you wouldn't go anywhere. Theoretically Troy, that method doesn't require you to do either first, as You can drive these trucks in FWD mode (although I've heard there are some interesting handling quirks when you do)

[troyboy162]

Rear wheel drive is the way to do it.

[4RunnerFever]

Heres a video showing the Toyota A-Trac 4wd system in action. Prado 120 and a 4Runner are the same except the prado is dressed up more. Same driveline design is shared in the all Toys,Lexus & Land Cruisers.

Ford Maverick is the Ford Escape in the USA. The last Lexus has a mechanical issue imo?
https://www.youtube.com/watch?v=CQPNH4XRbWA&index=31&list=FL2SxRHd1OA3rxWVT-5DeDLg


Another video with same rollers.
https://www.youtube.com/watch?v=KxiVNfwMp7A&index=35&list=FL2SxRHd1OA3rxWVT-5DeDLg