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Let me know if I am wrong:
I am cloudy on a few things. I believe when I hit the button that just the front left and the back right wheel have power and if the rear loses traction the front keeps the truck moving and that this is called full time 4w drive. If I shift the lever into 4H with locking center differential, than the front and rear will move at the same speed and not allow the front or back to move faster and this is called part time. Does the 4H with LCD make all four wheels have power or is it just still one in the front and back? Whats the advantage with LCD over just the push button mode (full time)? I have a good idea what the locking rear diff does, it basically gives 50/50 power to both back wheels but I always wonder whats going on with the front at the same time. Do the 2 front wheels ever have power at the same time. For instance lets say that I am in 4L with LCD or 4H with LCD, what wheels truly have power?
Thanks for the help. I am just getting started and I find it interesting but it can be confusing. I want to be confident in my ability to execute the right moves.
"I believe when I hit the button that just the front left and the back right wheel have power and if the rear loses traction the front keeps the truck moving and that this is called full time 4w drive."
full time means that the center diff is unlocked, and if you have open diffs front and back, then only one wheel will spin, if it looses traction (or if two wheels should both lose traction simultaneously, it is possible to spin both one on the front and back) but if 3 wheels have traction and one doesn't, then only one will spin. and you lose forward propulsion. Left or right isn't a factor, it's the traction (or lack of )that determines which wheel spins first. usually if you're already moving, your momentum may carry you to a different spot where the traction is better and the spinning tire may actually start to get traction
"If I shift the lever into 4H with locking center differential, than the front and rear will move at the same speed and not allow the front or back to move faster and this is called part time."
Yes this is part time, the front driveshaft and rear drive shaft, are now locked together, in the a similiar situation to above, the fronts will keep pulling should you lose traction on one rear tire
"Does the 4H with LCD make all four wheels have power or is it just still one in the front and back? "
all wheels get power (torque) until one loses traction, in Part time, you have to lose traction on the front and on the rear to get stuck (one side, doesn't matter which - if you have open diffs)
"Whats the advantage with LCD over just the push button mode (full time)? "
it guarantees that torque gets to the front and the rear, (full time has an open center diff, so you can get stopped with one wheel slipping
"I have a good idea what the locking rear diff does, it basically gives 50/50 power to both back wheels but I always wonder whats going on with the front at the same time."
Yes, the locking rear diff ensures that both wheels turn at the same rate. They're not getting the same power, because one could be on ice and the other on the road, so the torque or power is applied to the one on the road
"Do the 2 front wheels ever have power at the same time. For instance lets say that I am in 4L with LCD or 4H with LCD, what wheels truly have power? "
in any 4wd setting,(full and part time) where all the tires have traction, the wheels "have power" to use your phrase, the problems arise when one wheel loses traction, a normal diff will send the power, to the wheel with no traction, and the wheel with traction doesn't get any.
these days, there are several systems that deal with this issue, electric locking diffs, Limited slip diffs, viscious couplings (a sort of autolocking center diff) torsens, and wheel braking to create torque transfer (not so good for off road)
It works well off road, but the avid offroader should not rely on these, if you are gettting to a camp site 20 miles in on a dirt road that gets tough some times then you will be fine. But for people like me ARB air lockers are great, to get through mud you can not use te Trac system it will de-throttle the engine and you will get stuck, you need to keep the wheels spining a bit to get through it.
-Mike
99 Toyota 4Runner Limited:
center and rear diff locks and a push button full time mode
Thanks
"Anyone have an opinion whether to get a 1999 or 2000 year Landcruiser regarding the 4wd drivetrain. FYI: This will be used on and off-road; with the emphasis on off-road (gravel, dirt, mud, hills, general off-road travel...but not extreme off-road...not Rubicon!)"
It's almost as if there's a clutch mechanism engaging. No pattern - just happens about 2% of the time. Any insight? Thanks for any help.
It is my habit to put my Tacoma 4WD into 4WD high range when there is ice and snow on the highway. In places where there is alternating icy/wet areas, I'll still keep it in 4WD, as long as there is more ice than areas free of ice.
There will be no damage to the system as long as you are not turning sharply on pavement with a high cohesion (i.e. no ice), and that all four of your tires are the same size.
I've lived in snowy areas for more than 30 years and have never encountered drivetrain damage from this practice with any of my 4WD vehicles.
Four brand new tires and equally inflatted, maybe.
My question is what effect will adding a rear LSD have on the VSC system? VSC is disabled when you put in 4WD and lock the center diff since it can't apply brakes independently with power to at least one wheel on each axle (front and back). But If I have the center diff unlocked or I'm in 2WD what will happen? I'm stepping on the gas in 2WD and hit some gravel/mud/snow/ice and rear starts to swing out. The yaw sensors and everything else VSC etc. say HEY apply right rear brake only to make him straight. The new "mechanical" lsd says YO one wheel is spinning and the other is slowing down make those clutches grab tighter to put more power to that wheel that's going too slow. What will this do to the whole system? Clutch packs in LSD burn up? Brakes heat up and wear? ABS pump over heats? Throttle shuts off making spinning wheels null and void?
I know all the positive aspects of VSC and Trac and VSC will probably save MANY lives from stupidity accidents. I just HATE when I lose control over giving the truck throttle. Yes I know all of wwest's posts about letting off the throttle right away but off road/mud/snow/gravel/ice/steep hill are not always the best time to lose momentum or power to the drive wheels. A little extra spin of the tires to clear the sticky mud or snow from tread provides a new "clean" biting surface.
I have educated myself as to where, exactly, the ABS pumpmotor fuse is on my 2001 AWD RX300 just in case.
You can switch the Porsche PSM system off but it will come back on automatically if you get on the brakes, seems as close to a perfect VSC system as one can get.
Great explanation on the 4WD drive system.
I have a question for you re rear locking differentials. I have a 2005 SR5 4Runner with the V6. I only have a CDL, do you know if it's possible to install a rear locking differential? I don't plan on putting one up front, so I'd like to go the Toyota route instead of the ARB.
Incidentally, the new 4Runner replaces a Land Rover Discovery II (maintenance money pit). The Disco allowed you to lock the center diff without disabling ETC, (their version of the ABS torque-transferring technology) In an unplowed parking lot with about 8" of snow in it, I found that the 4Runner does better with VSC enabled than the Discovery did with ETC only. But that the Discovery did better with ETC and the CDL that the 4Runner did with the CDL, probably because VSC is disabled at that point.
My ideal setup would be VSC for most of the time while offroading (NJ Pine Barrens, mostly sand & mud) with the ability to lock up the center and rear differentials before hitting the rough spots. (3-wheel drive, essentially)
Thanks in advance for any information you can offer.
Jim
thanks for your help
jane
1) What are the long term problems that will manifest itself after doing this?
2) How should I test drive it when I get it back from the dealership?
2)Regular Check ups will be fine
AS a result something must "give", in most cases resulting in intermittent tire scrubbing or slipping to relieve the driveline "windup".
AWD, instead of having the center differential fully, "hard" locked, often adds a form of "rubber band", or partially, "softly", locks the center differential.
Here is my question. The SR5 comes with a stick to engage the 4WD (if you have a manual tranny) into 4L , 4H whatever you want.
Now, the LTD version also has a button on the dash that when pressed supposedly locks out the rr diff and makes it such that you would only drive with this feature on if you were off-road and going fairly slowly.
My question is: If i don't have that button option, then when I engage the 4wd, is it ALSO locking the rear diff to the maximum 4wd and therefore I too should not exceed that 15 mph speed and not drive as such on the pavement? In other words, If the LTD engages 4wd, BUT, driver decideds not to engage the button, can he drive it on the freeway at 55 in pouring rain like an AWD, but with my setup, I am precluded from that feature?
No one, including toyota, can answer that question for me. What is the difference in the "two levels" of 4wd on the LTD and which "level" do I get on my SR5 when I engage it?
thanks
"is it possible to install a rear locking diff?
Yes, generally,
but I don't know about 05's specifically, If it's available as an option, then one could conceivably get the Toyota parts and install them in their rig.
Regards
In short; you dont have the dial you dont have the locker. It will not and does not have the ability to lock your rear.
much control other than locking the center diff.
u probably don't want to lock ctr diff unless
you are stuck badly.
if yours is the multi-mode 4wd as mine, you
should be fine using 4Hi mode.
Check your mirror to make sure no one is behind you on a straight stretch and then test your brakes. Do an emergency stop. I think you'll find it's a whole lot more slippery than you thought.
General tips on snow: slow and steady. Avoid sudden inputs. Be gentle on throttle and steering.
In O/D the transmission actually acts as a torque DIVIDER, allowing the engine to rotate at the lowest possible rate, minimum frictional and pumping losses, at which sufficient torque is generated while still attaining optimal fuel economy.
In general O/D should never be used in high torque situations, pulling a load up an incline, or towing a reasonably heavy load for a long distance.
The above would be like trying to start ff initially in 3rd gear, too much torque required of the clutches so they slip.
Inadvertant use of O/D in high torque circumstances, as above, can lead to premature failure of the involved clutches.
I set the regular gears to neutral, then change the 4hi to 4low, but the low keeps poping up to neutral when I drive it at ~5mi/hr or more.
The seller said this is normal since I am driving it in paved road and not on sand/snow. Is that correct?
I do not recall having the central differential locked.
I do not understand why the low would pop up so quickly.
All help is greatly appreciated!
Fermin
I've looked at a number of vehicles and I am honing in on the 4Runner. Seems to have most of what I am looking for. Ride comfort, storage space, multi-wheel drive options, and enough room on the roof for my toys.
The question I have is which multi-wheel drive option would be best for me. My biggest concern is highway driving in the winter. The worst case scenario goes like this:
"You are driving on the highway during winter and it's snowing. There's a good 3" of the stuff and you are traveling on a 3 lane hwy. Everyone is driving in the middle lane and that is the most clear due to the traffic. The left and right lanes have snow and are rutted and slushy. You have a 6 hr drive to go and the guy in front of you is doing 40mph. You really want to pass but need to travel in one of the other lanes to do that. Getting into the lane is the trickiest part because you straddle good and bad road. Also pulling back into the center lane is tricky and traction while on the snow covered portion of road is dicey as well. I've done this in my Maxima but got a few more gray hairs in the process.
So the question is - Which option is best for this - 4WD or AWD.(I know I should just chill but I just can't guarantee it). I think AWD would be best because it's already on and it will do the adjustments. With 4wd I wonder how fast can you go and can you put in into 4wd while you are already traveling at 40mph. If 4WD would suffice for this I assume you would use 4H.
Can you share your experiences with this situation.
Thanks,
Jeffer
for the v6, switching from 2wd to 4wd can be done on the fly if you travel under roughly 60 mph. it may take a few secs to a minute for the 4wd to engage but there're tricks to make it engage faster that seem to work most times (accelerate or decelerate).
you can't go wrong with either v6 4wd or v8 "awd" on 4runner 2005. good luck.
My guess, from experience, is that you will likely never have occassion to shift INTO the 4runner's 4X4 mode while underway. 4X4 mode is excellent for getting underway initially, unstuck, but once underway you will always want to move into AWD IMMHO.
Still travel there, MT, in the wintertime rarely and am stuck with an AWD RX300. Don't dare venture out to the ranch but the RX suffices otherwise.
couple more questions so I know what I'm buying, Say you are cruising along on inclement roads but then hit some clear road, how fast can you go in 4WD mode? Can you do 80 mph? That's fairly normal speed at times.
No vehicle should be driven in 4WD, part-time 4X4, on a road with high traction. I'm using 4WD to mean a LOCKED center diff'l.
If you're using 4WD to mean the unlocked mode then fine.
but as I read in another post from wwest
#1741 of 1759 AWD/4WD by wwest Feb 17, 2005 (12:27 am)
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"4WD has a locked center differential which REQUIRES that the front driveline and the rear driveline ALWAYS rotate at exact the SAME rate. In a turn the front wheels take a different path than the rear and this will result in differing turn rotating for the dront driveline vs the rear rear."
Does this not make the 4wd different than AWD? I would think that if both front and rear wheels are forced to turn at the same speed that that could be a problem if traversing pavement with different coefficients of traction. ie going from clean road onto surface with snow and hence less traction. Or maybe it would actually be better. One thing I've found in slippery conditions is that you don't want to start sliding. Once you start you may loose control and then your goose could be cooked. Also on the 4R V-6 there was a button with a picture of the axles and drive train with an X between the front and rear. Does that unlock the Center Diff? If so what situations would be best for lock/unlock?
Basically AWD has some method of accomodating disparate front to rear rotational rates when they occur while at the same time apportioning engine torque front AND rear. No driver intervention required.
And now the confusion begins..
The earlier Jeeps, 85, 90, etc, had a simple 4WD mode using an open center differential. The only advantage it had was to evenly distribute torque as long as all tires had equal traction.
These Jeeps could also be driven in true part-time 4X4 mode, center diff'l LOCKED. 4X4 mode could be use in extra low gear range or in normal gear range.
It seems to me that everyone understands, has a mutually consistent understanding of AWD mode, and possibly 4X4 mode. The problem seems to be centered around poor understandings of 4WD mode.
Me included.
For what it's worth, here is how I have compartmentalized the various terms.
AWD: as described at the top.
4WD: a multi-mode full-time drive system that must be controlled by the driver, shifted into. Technically the same as AWD otherwise. The full-time 4WD mode of the 4runner is an example.
4X4: Part-time only, ALWAYS. Locked center diff'l and possibly front and rear diff'ls also.
Many folks use 4WD and 4X4 interchangeably and therefore the key is to have them define part-time or not.
But I don't think one needs to try to change what
4wd or 4x4 means, they are generic descriptions
Whether one says 4WD or 4x4, they usually mean they have one of the following.(or more if they have a selectable TC)
a Part-time system (for off road use)= locked center diff
a Full time systems (all wheels driven all the time) an open center diff
AWD Systems (2 wheels normally driven, and 4 if needed) Generally speaking, most AWD systems are essentially auto engaging (and dis-engaging) Part-Time systems
Further confusion is caused by marketing and by the fact some systems are multi mode... (could be any mixture of Full time/part time or AWD/part time
my grand cherokee is AWD, but with a TC with a locking TC for low range.
others (4x4s) have a Full time system with locking low (Discos and Merc MLs)