4x4 Auto vs AWD

[Thelt]

If you have the system that lets you pick between Auto, 4Hi and 4Lo then when in Auto it only engages the front wheels if it detects wheel slip from the rear.

If you have AWD it constantly sends power to the front on a 35/65 split, or something close to that.

Is that correct?

 

[techieman33]

yes

 

[velcrostrapshoes]

Ok well then what exactly is taking place when the 4x4 selection is set to 4x4 HI?

And is 4x4 lo a 50/50 split front rear?

 

[Curtis]

Yes I believe that is the case for 4x4 high and 4x4 lo
50/50 split

 

[velcrostrapshoes]

Yes I believe that is the case for 4x4 high and 4x4 lo
50/50 split

So high is 50/50 split 2? well what differentiates the 2?

I KNOW there is a difference because low wont even engage unless you're stopped and in neutral...


OH and while we're on the topic,.. Is it normal for there to be some clunking noises when coming in and out of the 4x4 modes? They don't really sound good..

 

[techieman33]

Ok well then what exactly is taking place when the 4x4 selection is set to 4x4 HI?

And is 4x4 lo a 50/50 split front rear?

4x4 should be a 50/50 split, low range has the same split but also will give also give you a lower (higher number) gear ratio. So it will go slower, and provide more torque which is useful if your crawling around on rocks, or trying to get yourself unstuck.

OH and while we're on the topic,.. Is it normal for there to be some clunking noises when coming in and out of the 4x4 modes? They don't really sound good..

yes some clunking is normal as the front axle engages or disengages

 

[GJarrett]

4 auto does engage your front very slightly even if your tires are not slipping. It does it at low speeds up to about 35~45 mph or so, and it is not much, but it does give a little power to the front. Once you get up in speed it lowers the input to the front axle until there is none at all. If your ABS module detects tire slippage then it kicks in it automatically all the way. This was discussed at length long ago on this site and I remember threads where technical links to how the system works were posted. I cannot remember who posted in those threads but you might try a search if you're curious.

I don't know exactly what you mean by 50/50 except to say that when it does kick in all the way it applies full power to both front and rear axles instead of full power to just the rear. It does this both in 4 high and 4 low.

And yes you'll hear a clunk when engaging and disengaging 4 wheel drive. You'll hear a click when engaging 4 hi but when you stop, go to neutral, and engage 4lo you're telling the transfer case to switch gearing and there's a very definate "clunk" sound and feel when you do that (and when you go back out of it to high gearing).

 

[Curtis]

So high is 50/50 split 2? well what differentiates the 2?

4x4 Low is a much lower gear ratio
You wont be able to go very fast in 4x4 Low.
I believe the manual tells you what the mph limit is in low.
Your truck will sound very loud because the engine will be at much higher RPM's while you move very slow.

Find a dirt road and give it a try. Don't do it on bare pavement

 

[GJarrett]

I found one of the old threads explaning 4x4 modes I told you about in the post I made above. Check out Tom Wilk's first reply in this old thread:

http://explorerforum.com/forums/showthread.php?t=10166

That should be a decent start to understanding what your different 4x4 settings are doing. I found the thread with the good 'ol search feature. There's a lot more threads you can find if you're curious enough. Hope that helps.

 

[E.B. Cornburner]

That's a great explanation of the Gen II Explorer's Control Trac system, but the Gen III gets even more complicated when in 4x4 Auto. They have a certain amount of "intelligent" or "predictive" action to them...For example, if you spin the tires in gravel when taking off out of a driveway and it engages the front axle, the system now knows that there may be a condition where additional traction is necessary, so even on dry pavement, it will engage the front end again if the throttle is opened beyond a pre-determined point. It will stay in this mode for several miles (10+) of driving in a no-wheelspin condition before it resets back to normal operation, or it can be reset if the key is turned off and restarted, or if 4x4 High is selected and then 4x4 Auto is selected again while driving with no wheelspin.
First time this happened to me, I was freaked out that all of a sudden I go to accelerate and the transfer case is engaging. It wasn't till I figured out how this system works that I got used to it.
When I got my PCM updated with all the current software versions not too long ago, I noticed that the 4x4 system now is not nearly as sensitive as it was at first. Now it seems to reset out of that "intelligent" mode much quicker all on its own. It now allows a little more wheelspin before engaging too. I can get a little chirp out of the tires on wet pavement before the transfer case engages, and I can't feel it engaging and disengaging at a certain throttle angle like I used to. Much improved if you ask me. I hated the way it was before, even though it was incredible in slippery weather. It was too much of an electronic "nanny" for my liking. I only like "idiot-proofing" to a certain degree before it just gets annoying.

 

[Thelt]

Most of the time I can not tell if mine is engaging or not. I know it has to be though because I can drive up my steep gravel driveway with no wheel spin where other rear wheel drive vehicles struggle a bit. In the rain it must be engaging too because I can tell the extra stability is there when I hit a puddle or something at speed.

I am happy with the way mine works but the other thread about saving gas by disconnecting the front drive shaft (which I am not going to do) made me curious about just how it worked.