Clint-
<font color=blue> think what he means by this is...it will "drag/skid."
Four wheel drive, on most vehicles, is not true 4wd.</font color=blue>
I certainly concur with your description of a "fully locked up" 4wd vehicle, and the technically correct description of how something in 4wd turns in to a 2wd without the use of a locker.
However, I'd go a step further and say that not most, but almost all vehicles sold on the lot today are not designed as "true" 4wd vehicles, as you put it. (I won't get in to the whole semantics stuff of are they "true" 4wd or not - I understand where you are coming from. 'Course taking it a step further, that means 2wd cars/trucks become 1wd vehicles at "loss of traction" point.)
Anyway, the only companies I know of that puts any type of locker in their "Joe Consumer" vehicles are Toyota and Jeep - Toyota with their TRD electro mechanically actuated locker (rear only) and more recently Jeep, with their ARB style air activated "Tru-Lok" on the Rubicon TJ (again, rear only.) Sure there are some limited slip diffs out there (Dodge, Ford, etc. all have them as an option), but a limited slip ain't no locker - not by a long shot - and when push comes to shove, a limited slip diff simply can't completely lock up the axle as a solid unit when all traction is lost on one side. (This isn't a bad thing, it's just the way they were designed - and, if you get down to it, when it comes to slick road travel at higher speeds, the limited slip is ***FAR*** safer than ANY locker (engaged) out there!) Again, there might be other companies out there putting in switched lockers or even automatic lockers I'm unaware of, but I'd bet that most of them are really limited slips - mainly due to the very odd handling characteristics lockers generate.
<font color=blue>Also, people who drive 4wd's in the snow often have difficulty because when the wheels start to spin the vehicle will not just have the back end come around (as in a rear wheel drive vehicle), but the whole vehicle will slide sideways.</font color=blue>
That assumes both the front and the rear have lost traction concurrently. I have been in circumstances where the rear end has "broken loose" but the front end retained traction, and, because the front axle was "pulling" (e.g. 4wd "mode"), it helped to right the vehicle before the back end came around. (Basically the same principle behind why front wheel drive cars are generally accepted as less likely to "get in to trouble" in slick situations than rear wheel drive cars - because you can “pull” the rear end “back in to compliance.”)
Can one "break" traction in both the front and the rear by over-accelerating in a "slick spot" with 4wd, thereby getting themselves in trouble? Sure. Does that mean 2wd vehicles are inherently "better/safer" in such conditions as was suggested earlier by another person? Nope.
I think the original post (by saw dust) on this thread was great - i.e. here are some descriptions of different types of 4wd systems. Helpful and informative. Unfortunately though, it seems like the subject of "benefits of 4wd or lack thereof" comes up every so often on TBN - someone throwing out some blanket statement about how 4wd is unsafe, unreliable, expensive to own/operate, poorly designed, etc. etc. etc.
If someone wants 4wd - fine. If they don't - hey, that's fine too. I've determined that folks who believe 4wd is a "bad deal" are unlikely to change their mind - for whatever reason. All I can do is point out what the manufacturers say and relate it to my own experience as someone who has owned & operated both types of vehicles, which seems to be in direct opposition to the original post I responded to. Frustrating for sure, but such is life. /w3tcompact/icons/hmm.gif
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Sidebar: The whole “drag/skid” thing becomes kindof complex due to the different types of lockers out there and the conditions in play - e.g. turning while increasing throttle, turning while “coasting”, etc. It also depends on which wheel (tire) you are referring to.
For example, the Detroit locker only engages under power and will "freewheel" the side that is exceeding the speed of the engine/transmission/transfer case. In other words, it acts much like an open diff at this point and allows each wheel to pretty much “do its thing.” Under power, however, things change significantly.
Assuming the locker is now engaged (I won't go through the whole non-locked to locked transition as it is very strange experience for the uninitiated), the “drag/skid” really isn’t accurate as it is more of a “peel out” that occurs. Since the wheel on the “inside” of the turn turn (e.g. right hand side if right turn, left hand side if left turn) is turning @ the same rate as the outer wheel (e.g. locker engaged), and since it has less distance cover, it is "peeling out" or spinning faster than the ground is passing underneath that side of the vehicle. (e.g. the outside wheel will not "drag" as it would be freewheeling, and the axle would therefore not be "locked up.")
On hard pavement, it can best be described as "chirping" sound. Of course that’s just Detroits - Lots of other mfgs. out there and different designs - some of which, if they act like a spool, may indeed lead to that "drag/skid" scenario under the right conditions. I guess my point is although it is probably beyond the scope of this thread, there are a lot more variables to contemplate about how “stuff” works and the effects different products/designs would have on a particular driving scenario. As they say, “The Devil is in the details.” /w3tcompact/icons/wink.gif
<font color=blue> think what he means by this is...it will "drag/skid."
Four wheel drive, on most vehicles, is not true 4wd.</font color=blue>
I certainly concur with your description of a "fully locked up" 4wd vehicle, and the technically correct description of how something in 4wd turns in to a 2wd without the use of a locker.
However, I'd go a step further and say that not most, but almost all vehicles sold on the lot today are not designed as "true" 4wd vehicles, as you put it. (I won't get in to the whole semantics stuff of are they "true" 4wd or not - I understand where you are coming from. 'Course taking it a step further, that means 2wd cars/trucks become 1wd vehicles at "loss of traction" point.)
Anyway, the only companies I know of that puts any type of locker in their "Joe Consumer" vehicles are Toyota and Jeep - Toyota with their TRD electro mechanically actuated locker (rear only) and more recently Jeep, with their ARB style air activated "Tru-Lok" on the Rubicon TJ (again, rear only.) Sure there are some limited slip diffs out there (Dodge, Ford, etc. all have them as an option), but a limited slip ain't no locker - not by a long shot - and when push comes to shove, a limited slip diff simply can't completely lock up the axle as a solid unit when all traction is lost on one side. (This isn't a bad thing, it's just the way they were designed - and, if you get down to it, when it comes to slick road travel at higher speeds, the limited slip is ***FAR*** safer than ANY locker (engaged) out there!) Again, there might be other companies out there putting in switched lockers or even automatic lockers I'm unaware of, but I'd bet that most of them are really limited slips - mainly due to the very odd handling characteristics lockers generate.
<font color=blue>Also, people who drive 4wd's in the snow often have difficulty because when the wheels start to spin the vehicle will not just have the back end come around (as in a rear wheel drive vehicle), but the whole vehicle will slide sideways.</font color=blue>
That assumes both the front and the rear have lost traction concurrently. I have been in circumstances where the rear end has "broken loose" but the front end retained traction, and, because the front axle was "pulling" (e.g. 4wd "mode"), it helped to right the vehicle before the back end came around. (Basically the same principle behind why front wheel drive cars are generally accepted as less likely to "get in to trouble" in slick situations than rear wheel drive cars - because you can “pull” the rear end “back in to compliance.”)
Can one "break" traction in both the front and the rear by over-accelerating in a "slick spot" with 4wd, thereby getting themselves in trouble? Sure. Does that mean 2wd vehicles are inherently "better/safer" in such conditions as was suggested earlier by another person? Nope.
I think the original post (by saw dust) on this thread was great - i.e. here are some descriptions of different types of 4wd systems. Helpful and informative. Unfortunately though, it seems like the subject of "benefits of 4wd or lack thereof" comes up every so often on TBN - someone throwing out some blanket statement about how 4wd is unsafe, unreliable, expensive to own/operate, poorly designed, etc. etc. etc.
If someone wants 4wd - fine. If they don't - hey, that's fine too. I've determined that folks who believe 4wd is a "bad deal" are unlikely to change their mind - for whatever reason. All I can do is point out what the manufacturers say and relate it to my own experience as someone who has owned & operated both types of vehicles, which seems to be in direct opposition to the original post I responded to. Frustrating for sure, but such is life. /w3tcompact/icons/hmm.gif
---------
Sidebar: The whole “drag/skid” thing becomes kindof complex due to the different types of lockers out there and the conditions in play - e.g. turning while increasing throttle, turning while “coasting”, etc. It also depends on which wheel (tire) you are referring to.
For example, the Detroit locker only engages under power and will "freewheel" the side that is exceeding the speed of the engine/transmission/transfer case. In other words, it acts much like an open diff at this point and allows each wheel to pretty much “do its thing.” Under power, however, things change significantly.
Assuming the locker is now engaged (I won't go through the whole non-locked to locked transition as it is very strange experience for the uninitiated), the “drag/skid” really isn’t accurate as it is more of a “peel out” that occurs. Since the wheel on the “inside” of the turn turn (e.g. right hand side if right turn, left hand side if left turn) is turning @ the same rate as the outer wheel (e.g. locker engaged), and since it has less distance cover, it is "peeling out" or spinning faster than the ground is passing underneath that side of the vehicle. (e.g. the outside wheel will not "drag" as it would be freewheeling, and the axle would therefore not be "locked up.")
On hard pavement, it can best be described as "chirping" sound. Of course that’s just Detroits - Lots of other mfgs. out there and different designs - some of which, if they act like a spool, may indeed lead to that "drag/skid" scenario under the right conditions. I guess my point is although it is probably beyond the scope of this thread, there are a lot more variables to contemplate about how “stuff” works and the effects different products/designs would have on a particular driving scenario. As they say, “The Devil is in the details.” /w3tcompact/icons/wink.gif