Basically, the difference is how the power is transferred. Remember it is called a transfer case. (4X4=How power is transferred, front to back) 4X4 low Range is in a lower ratio, as well as, having the front wheels move at different ratio than the back. The front is actually moving faster than the back hintz, the grabbing power and low range movement of the reason (4 low) was made (to get you were you are going over many obstacles when maximum traction is needed). The reason that you cannot run (4 low range) on the road is because it causes axle bind. This is caused by the front moving at different speeds than the back. Also when you turn the front moves well more than the back. With no forgiveness in the drive lines and transfer case it causes everything including, Driveline, Transfer Case, Axles to bind up hintz the word *Axle bind*. Look at the picture below. As a truck turns the wheels are locked in but moving different revolutions than each others.

Green= Back wheel movement on turns
Blue= Front wheel movement on turns

Also look at each wheel and the difference between how far they move. This is what causes axel bind. Remember they are locked so how is this done?

Answer: Each of the wheels can slip on loose surfaces diminishing any *Axle Bind* from being present.

This is a good example of how *Axle Bind* is created.

Also remember the lesson about the front wheels moving faster ratio’s than the back for maximum traction, due to the (transfer of power). This also causes *Axle Bind*. But moving strait down the road. This brings the subject to light.

Now how can we have 4X4 on hard non slip surfaces?

Answer: Incorporated into the transfer case are different ways to deal with power transfer.
1. Strait power transfer with slip. AWD, 4-HI
2. Power transfer without slip. Part Time, 4-Low
3. Power transfer to rear wheels only. 2-Hi
4. No power transfer. Neutral

The main difference between AWD and 4-Hi is how the transfer case works and wheel spin.

[IMG]local://upfiles/17201/31729CEB06004D1EAA357EEE69CAF3E7.jpg[/IMG]

 

To add more lameman's light to Hydra's explanation, the terminology of AWD is where the transfer case automatically transfer power from the wheels that slip to the wheels with traction. Perfect example is watching those subaru ad's with their acclaimed AWD drivetrain. AWD tranfer case manages traction and slip control with no manual intervention.

The terminology of Full Time 4x4 is similar to AWD with the exception that the user has custom control of managing the traction and slip control of the transfer case.

So I think this is the differences between AWD and Full time 4x4 in a lameman's nutshell are this;



Full time 4x4 modes:

Normal AWD mode (Transfer case allows main drive line differential slipperage between front and back drivelines) ---> differential sliperage prevents axle binding as Hydra stated. Can be driven on any type of surface wet or dry.

Locked 4WD high (Transfer case locks main drive line differental to match both front and rear drivelines) ---> can cause axle binding if driving on dry, hard, flat surfaces. Only used for wet or where light traction is needed. Not intended for use for long extended time period.

Locked 4WD Low (Transfer case locks main drive line differental to match both front and rear drivelines) ---> can cause axle binding if driving on dry, hard, flat surfaces. Only used for areas where maximum traction is required and should be used only for a very short time period.

Neutral



AWD 4x4 mode:

Normal AWD mode only




The front and rear drivelines have limited slip axles also for both AWD and full time systems. This will let the outside wheel turn faster than the inside wheel when you make turns so it will not bind the axles. Only the Full Time 4x4 drivetrain can control the axle slipperage of the front axle. (Remember the old days when you have to get out of your truck and manually turn the lock to lock the front wheels to the axle?) When driving in locked 4wheel high or low, the front tires spin the same rotation. when making a turn, you can definitely feel the front wheels fighting each other and causing a bind on the front axle.

As far as the front driveline spinning faster than the rear driveline, I think this application only applies to part time 4x4's because with Full time or AWD, both drive lines must have equal gearing in order to run in full time or AWD mode, unless the transfer case is the device that can alter the difference in gear ratio between front and rear drivelines.

 

Pretty close guys... in fact close enough for government work.

Just note that on the FT4x4, there is *NO* AWD notification or verbiage. The transfer shift says 4x4, 4x4high, 4x4low and N. Nowhere does it say AWD. Also, when in 4x4 high or 4x4 low the 4x4 light on the dash is illuminated. When in normal driving mode of 4,x4 the dash light is not on. Finally, this is applicable on '98-'00 years only. After '00 and starting with the '01, DC called the system AWD and for the most part made the changes you mentioned above.

Good work.

IndyDurango

 

Also remember that there were two different systems to chose from. R/T models had AWD and others. But the SLT+ version in 1998-1999 came equiped with the choice of 5 different transfer case settings. The FULL TIME 4 Hi was built for all road surfaces unlike the AWD that changes to the wheels that grip, but in the same instance they are close to the same. Now for the main point I was getting at is the PART TIME 4 Hi. This is locked just like the 4 LOW. This is why it is forbidden to drive on all road surfaces and should only be used when needed. VERY LOOSE SURFACES ONLY!!!! Be very careful while using PART TIME 4 Hi.

TY for those postings guys.

 

this is alil confusing to me.
i have a 99 Durango 5.9 slt 4x4.
my transfercase has these options: 4x4PT, 4x4hi, N, 4x4lo.
what conditions are ideally suited for using 4PT over 4hi? when would you use 4hi over 4pt?
i just bought this truck used and was also wondering what axles are on them?? what type of lockers are available? what lockers are you guys using? what do you recommend?

i mainly need 4x4 for driving around my property. it's muddy as heck in the winters and my driveway has steep inclines with ruts and dips everywhere.

 

hmmm looks like i am going to have to look and my t-case lever again, i swore it had 2 hi 4 hi and 4 lo.

 

this thread is talking about the four wheel drive. of course i have 2hi......

 

So restless, which one is it 2WD or 4WD? when you say 4x4PT, are you referring to 2WD?

Your question about when to use 4x4PT or 4WD Hi is confusing me.

As Hydra, Indy and I have explained, the only time you need to lock your transfer case to 4WD high is to maintain total control of the 4 tires simultaneously when dealing with surfaces that can cause any and/or all 4 tires to easily loose traction. This applies to 4WD Low also. High or low, both modes locks the front axle where both tires will spin at the same rotation.

4WD high/Low (locked) forces both front tires to turn the same rotation. Thus you get axle binding when making turns (outter tire turning faster than inner tire on the same axle). Also, on some older generation 4x4's (not sure if this still applies today), the front axle has a slightly higher gear ratio than the rear axle, thus causing a bind in the transfer case. So you can imagine that you can have one or two areas where binding can occur and shorten the life of the drivetrain if you were to drive your vehicle in 4WD locked mode on normal dry surfaces. When driving in snow or wet surfaces, this allows you the drivetrain to have some slipperage but still maintain traction. But this mode should only be used for short term as binding on your drivetrain components still exists. I am sure you have experienced your D doing its jerky jerky motion when trying to make a turn from a standstill. The jerky jerky motion is caused by the front tires as the inner tire is spinning same rotation as outter tire. As the inner tire has a shorter distance to travel, it is trying to outpace the outter tire.

With AWD, as simply as Hydra put it, functions similarly to full time 4WD but it can transfer power to the wheels that are not slipping. Full time 4WD does not really do this. It is just 2 sets of axles turning instead of one axle with each axle having limited slip gearing so one tire on the axle can spin faster then the other tire. (example of this is when you are making turns). No binding to the axles or the transfer case when driving on normal dry surfaces.

Binding on full time drivetrains only occurs at the transfer case if driving on certain surfaces where it causes one of the axles to completely loose traction (front or rear). A situation to fit this scenario would be climbing up a hill in normal F/T 4WD mode. The front or rear axle can lose traction at any moment and cause severe binding on the transfer case. These occurances are often rare. When having to deal with these types of surfaces, that is when locking down your drivetrain comes to play and is very beneficial and has advantages over normal F/T 4WD mode.

Hope this sheds some light at the end of your tunnel.

For me, the only time I force my Durango R/T to go from Normal 4WD to locked 4WD high is when I am driving on icy roads or roads layered with heavy snow. Otherwise, I stay in Normal 4WD.

 

I think he is referring to the difference between 4wd Part time and 4wd Hi. The difference is simple. 4-Hi will allow for some slippage in the transfer case thus not allowing axle bind. (Like it says 4wd Hi is for all road surfaces.)

4wd Part time is only for very slippery conditions as there is no slippage in the T-case. If you run in 4wd Part Time on hard surfaces it will cause axle bind and BLOW your T-case. Both are 4wd Hi Range but slippage in the T-case is the difference. The R/T models didn't come with this option. The only time you should run 4wd Part Time is when you absolutely need it! (Thus is why it called Part Time.)

It acts like 4-Low but gives you more speed and the same maximum traction. Also from what I've read some how distributes power differently to the wheels. But no conformation on that!

 

Hydra, that defintition still don't ring with me. (4wd part time vs. 4WD high that is). Actually both of them to me, have no correllation to each other.

4WD High should be referenced as locked mode. Same definition for 4WD Low. Both these modes references when you have to manually put your vehicle in this mode for part time or temporary use when you need maximum traction to meet the current road conditions. Both of these modes are available on Part time and Full time 4WD systems.

I think the correct wording restless is trying to ask is differences between Full time 4WD and 4WD high (locked) modes?

Example: This is what I see on my Durango full time transfer case lever:

4WD Low
Neutral
4WD
4WD high

What I see on my buddy's part time transfer case lever:

4WD Low
Neutral
2WD/Normal
4WD High