Question from a "non mechanic"

I know it wasnt totally true..My brain isnt working right now. What I'm trying to do and say, and what comes out, isn't the same..lol

 

I get that too,,,LOL

 

It's been like that since monday. I need a vacation, badly.

 

Using 4HI on pavement is fine if wet and you go strait. Remember to return to 2HI before turning. Some will differ with this opinion.

I use this some months to exercise the the 4x4 for 10 miles a month.

You can feel the binding when turning in 4HI on paved road to too hard dirt road. Once you feel the binding you know it is not too good.

Some people say never put in 4HI even when wet and going in a strait line. Owner has to decide.

 

AWD- No driver interaction. Always in full time all wheel drive.

4WD- Driver can select between 4x4 or 4x2.

Both may have a high and low range selectable transfer cases.
Although, passenger cars/ sports sedans with AWD won't have a transfer case.

 

If you have the stock Dunlops I doubt you'd hurt it running 4WD in the rain if driving in a straight line. Just pick a pedal and push it while in 2WD, don't matter which, one of 'em will break loose really easily... no way can the drivetrain bind up with tires that bad!

I wish Toyota would copy GM a bit in the transfer case regard. 2HI-4AWD-4HI-4LO has been available in their SUVs for years and would be really great with this truck's featherweight posterior.

 

good lord..great explanation..i was still forming words in my feeble brain.

 

CENTER differential

A center diff on AWD vehicles will allow the front and rear axles to "differentiate" or slip, in the same manner the front or rear axle allows the tires on the respective axle to turn at different rates. Your front and rear sets of wheels will not spin at the same rate through a corner, thus the need for a differential. A selectable transfer case will lock both axles together, turning at the same rate, regardless of outside forces, if the wheels aren't allowed to spin easily like in soft dirt, mud, snow, ice etc... you feel binding until something breaks or the wheels hop/skip on the pavement.


OH, and a differential allows you to apply equal power to two wheels on the same axle (given equal traction at both wheels) but yet be able to apply power and allow the wheels to rotate at different speeds as you go through a corner.


Just for reference...
An open differential will send power to the wheel easiest to turn. If like on a dry road, both wheels have equal traction, it will send equal power to both wheels.


Now try to figure out how the spiders walk inside the carrier when you turn.

 

This has been explained pretty thoroughly already, but basically the easiest way to explain it, is that when you go in to 4WD one front tire and one rear tire (whichever ones are easiest to turn) are going to spin together at the same rate when you hit the throttle. When you turn one tire has to spin faster than the other to make the turn because they follow separate paths around the corner. 4WD won't allow them to do this though since they have to turn at the same rate and this causes the binding. If all of your drive train components are stronger than the force required to break traction of the tires all the time you could drive around in 4wd all the time, but as a precaution it is recommended that you don't because you could damage something.

Another thing with being in 4WD on pavement is that not all 4 of your tires are the exact same diameter and each tire will have slightly different rpms at any given speed. At low speeds this is insignificant, but going down the freeway in 4WD (even driving straight) there could be enough of a difference to possibly cause some stress on the transfer case and axles.

 

Kirk's video is the best to understand what a differential is. This understanding is crucial to understanding the 4wd system

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

 

Dont forget that an AWD will become one wheel drive when stuck in the sand because of the center diff Also some 4x4s do have a center diff like my jeep commander. But that has an electronic locker. So there are exceptions.

I agree, and do the same. Not a lot of places where I can drive off road for 10 miles around here.

Not every 4wd.

 

If I take away the right stuff here, its not binding because the front two wheels are fighting each other, its binding because the front is fighting the back. Its not the lack of a front diff, its the lack of a center diff which would allow the front and rear shafts to be independent. I didn't realize that AWDs had three diffs. Thanks a lot guys--I learned something that has bugged me for a while!

 

Yep. Sounds like you have it figured out.

And just in case, not having a center diff isn't a down side. Like was stated earlier, if you have a center diff that means that if you get stuck power will only go to 1 tire (the one with the least traction). Without a center diff it will go to 2 tires. One in front and one in back, so it is harder to get stuck.

 

Yep, then you need a center diff lock.

 

some good info on this subject in the links below...

 

read these 2 links...
http://www.4x4abc.com/4WD101/def_turnpart.html
http://www.4x4abc.com/4WD101/def_turnfull.html

 

The confusion all we dummies have had on this subject is this: The problem is not that the front wheels can't turn at different speeds, but that the front and rear drives cannot turn at different speeds...that is, its the transfer case between the front and rear that limits your functionality . When the simple transfer case becomes a differential, you are starting to get into AWD territory....

 

center diff lock might just be a little bit relevant