Understanding 4WD

[Snaggle]

I have a '03 Z71 and live in MD. Though I previously owned a '88 Chevy S10 Blazer 4x4. I find there is no comparision between the 2. I have read the other posts about 4WD and found them to be interesting and very informing to the point where they were almost too technical. I realize that true 4WD is not feasible because turning would be extremely difficult, but regardless of 4HI, 4LO or "Auto" do all 4 wheels actually engage and turn when slippage is detected at the wheel or is it more like AWD and only the wheels not spinning freely recieve the power to give the truck the ability to move and turn. Secondly, how does a Limited Slip in the rear work when in 4WD. Is it by passed and both rear wheels receive full power or would like the passenger rear wheel receive power and then lock in the driver's. Perhaps some plain insight to this would be helpful. The way I see it (or think I do) for Arguments sake: When in 2WD the Rear Passenger Tire would engage - if it slips - then the limited slip would engage the driver's side up to 20 mph. When in 4WD would one Rear Tire engage and the opposing Front Tire and when either begins to slip the opposite tire on the same axle then engage? I realize this is a confusing post but I have never seen all 4 wheels spin when in 4WD - of course I'm always behind the wheel (steering). I guess I'm asking for an order of operation or assemblance. Thanks to anyone who can make sense of this to respond.

 

[RichUF]

These two basic articles on the subject really helped me out a while ago when I was searching for this info. The Av is my first 4WD

http://auto.howstuffworks.com/four-wheel-drive.htm

http://auto.howstuffworks.com/differential.htm

As far as specific to the Av, my understanding is that the front two wheels can not both spin...there is an open differential between them. The back two wheels can if you have the eaton G80 locker option (or standard with Z71). Therfore, there is only potential really for three wheels to spin with a Z71 (or base 4X4 w/ locker), and a base model 4X4 w/ locker can really only spin two

I hope that is mostly accurate, and there are plenty of very experienced 4X4'ers around here who will likely be along to give you a better answer.

Rich

 

[bekind]

Just as Rich said, if you have the locker you have the ability to power a single front wheel and both rears in certain situations. Think of it this way, without the locker, power will drive the wheel with the least resistance in the front and rear, basically powering 2 wheels. Throw the locker in and you can temporarily power both rear wheels because the differential has locked, this only occurs when the rear wheels begin to spin at differing RPMs. However, you will still only ever be able to power a single front wheel in the current setup. Things you can do while 4x4ing is using the brake and trying to trick the spinning front wheel and hopefully sending power to it, this does not always work however, but worth a try if you are stuck.

~bekind

 

[sthomp]

Not to confuse snaggle, but it is possible to spin all four wheels without a locker in either axle assuming traction is equal for both tires per axle. Its just that the majority of the time you are seeing tires spin you are stuck or typically in a situation where traction is biased to one side of the axle. Normally you do not want a locking differential in the front axle unless you are driving at very slow speeds as you lose the majority of the steering, thats why many people use an air locker in the front to engage and disengage the lock mechanism on demand. hope this helps.

 

[bonedog]

I have been looking into the Eaton EZ lockers for the front and rear of my AV. Not that I do any severe offroading but for that one time when I needed a locker(shut up Glenn) I could have used it. I would rather know its there and never use it then not have it at all and wish I had it when stuck.

 

[Snaggle]

As far as specific to the Av, my understanding is that the front two wheels can not both spin...there is an open differential between them.

So what you are saying if I understand this, is that one and only one wheel will recieve "power" or is it that either wheel can receive "power" just not simultaneously. And the Back axle works the same it just has the locker so both wheels receive "power"

 

[RichUF]

So what you are saying if I understand this, is that one and only one wheel will recieve "power" or is it that either wheel can receive "power" just not simultaneously. And the Back axle works the same it just has the locker so both wheels receive "power"

front: either will CAN, and both can simultaneously (I think) until one loses traction completly, at which time you're done (with forward progress from the front wheels, that is)

back: locker means both wheels CAN lock up and receive EQUAL power.

 

[Snaggle]

RichUF

Thanks for the website links - I've used that website before and should have thought of it myself. They provide good clear information written in common tongue. So I guess the last question I would have to fully understand the potential of my beast would be: "Is the front differential an Open Differential (which I believe it is ) or a Limited-Slip Differential (which I unfortunatly don't think it is).
According to the links that you recomended an open differential was used on older trucks and SUVs and the limited-slip is used on modern. (I could only hope). I have tried other web sites for the specs of the transmission and 4WD but nothing states exactly what is mounted below.
Though I did own a S10 with 4WD - I feel this AVy out performs that one by a long shot. But that could be due too many factors (weight, locking rear, tires, etc.)
Once more thanks for your insight - this is why I feel this is a really beneficial web sight.

 

[sthomp]

snaggle,

the front differential in the av is an open differential, which is your everyday variety found in most vehicles. It is rare to find a vehicle with a traction aid in the front diff because it is so critical to steering/safety. if you do see them offered from an auto manufacturer it will likely be an "on demand" locker that will function as a open diff normally and lock when traction to both tires is needed...i think land cruisers and rovers are some that offer this option from the factory.

as far as the components in your av, here are some links that should tell you all you need to know.
transmission(4L60E):
http://www.gm.com/automotive/gmpowertrain/transmissions/hydra/apps/4l60.htm

transfer case (New Venture 246):
http://www.newventuregear.com/tcases.html