99 4WD Drive Train Questions/Information

i can't comment on the toyta center locking diff but i'm pretty sure it has a vc and is not truely locked ..

but i'll concede to other on this and many other points ;-)

just wanted to reiterate this .... ;-)

but i still think i was right in comparing the locking center to a true 4x4 set up and normal 4wd mode to AWD on our 4runners, it's kinda cool it's chain driven instead of having a VC (jeeps np249 and other t-cases have a vc which breaks around 90K)
 
I think having the center locked is not too much a big deal like you said Martin. Or atleast when you are not on dry pavement.

Its just when taking those tight switchbacks with the wheels fully cranked that I think hmmm is this trail loose enough or am I going to get stranded at 13,000 feet! Most of the trails I am on are rock and dirt but some are bigger flater rocks that are dry, and it seems that in that case I may damage something... I guess Toyota designed it to be resilient.
 
Full time 4wd, via a center diff, and AWD, like a Subaru, are NOT the same, they are not even close. If you want to think of them as the same feel free, but when you talk to people who actually know they will think you are ignorant about vehicles.

As far as one slipping tire leaving you stranded that is not the case. As I mentioned earlier, you still have 2 open diffs, and you can still spin 1 front and one rear. So if you are in 4hi center unlocked and you rear drive tire is on ice the front drive tire will still pull you off. Now if one rear and one front are on ice you may be stranded, but locking the center diff will not help in that situation, you still only have the ability to send power to 2 wheels, 1 front 1 rear. In the above scenario you'd be hoping your TRAC system would hit a brake and push power to the opposite tire, or you lock the rear diff, if so equipped, and move on.
 
As far as one slipping tire leaving you stranded that is not the case. As I mentioned earlier, you still have 2 open diffs, and you can still spin 1 front and one rear. So if you are in 4hi center unlocked and you rear drive tire is on ice the front drive tire will still pull you off.

I dont think so, not with the center unlocked. This is not the torsen type center diff that can send a percentage to the front and a different percentage out back.

Now if one rear and one front are on ice you may be stranded, but locking the center diff will not help in that situation, you still only have the ability to send power to 2 wheels, 1 front 1 rear. In the above scenario you'd be hoping your TRAC system would hit a brake and push power to the opposite tire, or you lock the rear diff, if so equipped, and move on.

Right, youd still be stuck, but he cant rely on TRAC as he has a 99 and that didnt come out till 2001.
 
Its just when taking those tight switchbacks with the wheels fully cranked that I think hmmm is this trail loose enough or am I going to get stranded at 13,000 feet! Most of the trails I am on are rock and dirt but some are bigger flater rocks that are dry, and it seems that in that case I may damage something... I guess Toyota designed it to be resilient.

No, two points:

First of all, if you are on a tight trail with switchbacks, you're going to be bouncing up and down at some point (unless you have found some amazingly flat trails!) Just lifting one wheel a fraction of an inch off the ground will allow it to "slip" enough to relieve any binding or pressure. And that's likely to happen 50 to 100 times (or more) for every mile of trail you run.

Second, it's not like one little bit of pressure and your axle or driveshaft will snap without warning. It takes a lot of stress over a long period of time for something to fail.

As I said, when you are running with your center diff locked, your vehicle is in the same position as every Jeep, Blazer, Bronco, FJ40, Tacoma, etc with conventional 4wd. If they don't break axles from driving on trails like that (they don't) you don't have anything to worry about.
 
Full time 4wd, via a center diff, and AWD, like a Subaru, are NOT the same, they are not even close. If you want to think of them as the same feel free, but when you talk to people who actually know they will think you are ignorant about vehicles.


i think your getting confused about my statements as branding,

4x4 is a true 50/50 power split front to rear, call it 4lo,center diff lock, 4x4, whatever

awd/full time 4x4/4hi, allows for power transfer from front to back.allowing
a differential in speeds around corners (slippage)
call it awd call it quadratrac call it 4hi whatever you want and achieve it by mech or fluid transfer devices it still has the same end results even though it functions a bit differently.


you can either be locked front to back(4x4) or side to side(locked front and rear diffs) anything else would be a form of AWD or fulltime to allow slippage,
for driving on pavement.

i think my statements were to general, as i get what your saying
a lsd is not the same thing as a locker even though for design purposes they are the same, as they both achieve the same outcome by different means.
and yes they do achieve the same thing, and yes they both have their built in pro's/con's from the way they derive that outcome.

they make it really confusing with branding and how different companies go about it, but in the end like i said above there's only 3 forms of 4x4 and how different companies go about it is a completely different topic.

the 3 forms of 4wd
4x4 50/50 power split front rear (off road only)
awd 60/40 power split with power transfer for slippage for pavement driving
4x4 fully locked 50/50 front rear 50/50 left right

yes over simplified but still correct.(unless i'm still wrong?)
 
the 3 forms of 4wd
4x4 50/50 power split front rear (off road only)
awd 60/40 power split with power transfer for slippage for pavement driving
4x4 fully locked 50/50 front rear 50/50 left right

yes over simplified but still correct.(unless i'm still wrong?)


I would have to make an argument for a 4th category, full-time 4wd. Right now you kinda have it lumped in the awd category.

The 4hi mode of a Torsen t-case 4Runner is more akin to an old Chevy truck or Jeep sporting a NP203, full-time 4wd t-case. Most, modern awd cars do not have a full, gear driven, mechanical connection for distribution of power front to back. They use some type of viscous coupler, hydro/electric clutches etc. This helps to explain CRV's, Pilots, Olds Bravadas and other awd drive cars getting significantly 'outwheeled' by a T4R in 4hi (even when clearance isn't an issue).


In an effort to debunk what I've just said someone might ask, "well, what's an old Subaru?" This is where it gets grey... A while back anything that didn't have a low-range was considered awd. Back then by stating a vehicle had full-time 4wd vs. awd implied a t-case that could be locked (front to back, fixed 50/50 distribution) and had a low range. I think that still holds true for most. The old Suby or some of the old Jeeps CJ's w/a one-speed, full-time 4wd could be considered awd, IMHO, in spite of the fact there's gears not clutches dividing the torque.

That’s my 2cents and overall I agree with you. I just think AWD is a bit too broad of a term and it doesn't imply the off-road prowess a full-time 4wd mode implies.

:cheers:
 
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I dont think so, not with the center unlocked. This is not the torsen type center diff that can send a percentage to the front and a different percentage out back.



Right, youd still be stuck, but he cant rely on TRAC as he has a 99 and that didnt come out till 2001.



Its not about sending a different percentage front to back, its about being in 4wd and having 2 drive tires at any given time. You are thinking the center diff changes the function of your front and rear diffs, which it will not. One tire losing traction w/ the center unlocked will not leave you stuck, it will only effect the other tire on that axle, the opposite axle will still have power.
 
Its not about sending a different percentage front to back, its about being in 4wd and having 2 drive tires at any given time. You are thinking the center diff changes the function of your front and rear diffs, which it will not. One tire losing traction w/ the center unlocked will not leave you stuck, it will only effect the other tire on that axle, the opposite axle will still have power.

While in 4WD with the center diff unlocked, you do not have 2 drive tires at any given time. You only have 2 drive tires at any given time with the center diff locked. The center diff does not change the function of your front and rear diffs that is true, but one tire loosing traction with an open center diff (not torsen) will send all power to the wheel with the least traction, therefore you will be stuck.
 
While in 4WD with the center diff unlocked, you do not have 2 drive tires at any given time. You only have 2 drive tires at any given time with the center diff locked. The center diff does not change the function of your front and rear diffs that is true, but one tire loosing traction with an open center diff (not torsen) will send all power to the wheel with the least traction, therefore you will be stuck.



Well my experience with my 02 tells me different, but you believe what you want.
 
Well my experience with my 02 tells me different, but you believe what you want.

So can you further clarify your below statement then...In particular the bolded statement and explain how that center diff unlocked situation differs from your explanation of the center locked scrnario. You are saying the front tire will pull you off in both the locked and unlocked scenarios (front tire on dry road, rear on ice), then how are they different and what is the pourpose of being unlocked...remember the OP's 1999 doesnt have TRAC like yours does.

pat161 said:
As far as one slipping tire leaving you stranded that is not the case. As I mentioned earlier, you still have 2 open diffs, and you can still spin 1 front and one rear. So if you are in 4hi center unlocked and you rear drive tire is on ice the front drive tire will still pull you off. Now if one rear and one front are on ice you may be stranded, but locking the center diff will not help in that situation, you still only have the ability to send power to 2 wheels, 1 front 1 rear.
 
Having a Center Diff Lock and a Rear Locker factory ?

It appears that all of the 99 Limiteds and all 2001-2002 models have the center diff locks....(since the 2000 year ltd didn't differ from 1999) from top4runners.org.. "A center differential lock switch has been provided in the instrument panel so that the locking and unlocking can be controlled by the push of a button, rather than through the 4WD shifter"r. Toyota 4Runner History 2001

so if one wanted BOTH a rear locker and center diff locked 4runner factory equipped it would be have to be in the 1999-2001 model years since they didn't offer the rear locker in 2001-2002

or...you can get a 2001-2002 with the center diff lock and add the factory rear electric locker from a 99/2000 year...
 
It appears that all of the 99 Limiteds and all 2001-2002 models have the center diff locks....(since the 2000 year ltd didn't differ from 1999) from top4runners.org.. "A center differential lock switch has been provided in the instrument panel so that the locking and unlocking can be controlled by the push of a button, rather than through the 4WD shifter"r. Toyota 4Runner History 2001

so if one wanted BOTH a rear locker and center diff locked 4runner factory equipped it would be have to be in the 1999-2001 model years since they didn't offer the rear locker in 2001-2002

or...you can get a 2001-2002 with the center diff lock and add the factory rear electric locker from a 99/2000 year...

Rear and center lockers only came on 1999 and 2000 models. For 1999-2000 models, push the button for unlocked 4WD (unlocked center diff), slide transfer case to 4HL for 50/50 4WD split (use only on loose terrain, center diff locked)

For 2001-2002 models, the push button enables unlocked 4WD to be used on dry pavement (same as 1999-2000 Limited models). Hitting the center diff button is equivalent to sliding a 1999-2000 transfer case into 4HL. Hope this helps
 
So can you further clarify your below statement then...In particular the bolded statement and explain how that center diff unlocked situation differs from your explanation of the center locked scrnario. You are saying the front tire will pull you off in both the locked and unlocked scenarios (front tire on dry road, rear on ice), then how are they different and what is the pourpose of being unlocked...remember the OP's 1999 doesnt have TRAC like yours does.



Perhaps I don't really understand what you are saying, to me you are saying that when you put an 01 or 02 into 4wd center unlocked you are not in 4hi at all, any situation that would result in a stuck in 2wd would still result in the exact same scenario in 4hi or lo center unlocked. I can reverse your question and ask why bother putting my truck into 4hi center unlocked at all if it is the same as being in 2wd? I was under the impression the center diff alowed slippage, not guaranteed it.
 
i get a big smile ear to ear when i get to play with all of the modes in my '99,

awd (yeah i know not a subie)lol,center diff locked, rear diff locked, sooo bad ass!
 
Rear and center lockers only came on 1999 and 2000 models. For 1999-2000 models, push the button for unlocked 4WD (unlocked center diff), slide transfer case to 4HL for 50/50 4WD split (use only on loose terrain, center diff locked)

For 2001-2002 models, the push button enables unlocked 4WD to be used on dry pavement (same as 1999-2000 Limited models). Hitting the center diff button is equivalent to sliding a 1999-2000 transfer case into 4HL. Hope this helps

kelly-

ok yeah...that does make sense...I obviously don't own a 4Runner yet...so I've been reading these forums inside and out learning about 'em....appears what I want is either a '99-'00 Limited or '01-'02 any model and I'll have the multi-mode and a good 4wd system...

I found an '02 Sport for about $ 11 k with 115 on the odometer...trying to get in touch with the guy to ck it out! Xmas present for me!
 
Perhaps I don't really understand what you are saying, to me you are saying that when you put an 01 or 02 into 4wd center unlocked you are not in 4hi at all, any situation that would result in a stuck in 2wd would still result in the exact same scenario in 4hi or lo center unlocked. I can reverse your question and ask why bother putting my truck into 4hi center unlocked at all if it is the same as being in 2wd? I was under the impression the center diff alowed slippage, not guaranteed it.

You gain an advantage over 2wd because if both the front or rear wheels are getting the same amount of traction, but the front or rear is losing traction, then the 4wd(unlocked) will shift power to the end that has the least traction. This is the case most commonly encountered for 4wd(unlocked) ie AWD such as when leaving from a stop during wet or snowy/icy conditions in a straight line.
In on road situations you rarely lose complete traction on one end of the vehicle, or even on one tire on an axle, it is usually only a small amount of slippage which only causes a small shift of power. In any situation where complete loss of traction is encountered, all power is shifted, which is actually unwanted in those cases. This is also why these types of systems are significantly lacking for actual offroad purpuses when unlocked.
 

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