Difference between part time and full time 4X4

[sreilly77]

With Part-Time 4WD on the front wheels are forced by good traction on the ground to rotate faster than the back tires. Since the front drive shaft gives the same RPMS as the rear tires, there is then a fight between the front wheels and forces coming from the front drive shaft. This results in the slowing down of the front wheels, which can lead into very wide turns and very heavy understeer. Therefore in time your front wheels don't pull like they should when you put your Jeep in 4WD. You could end up with axle binding and the Jeep can get stuck in 4WD or become very difficult to release back into 2WD.

In the end, the gears in the diffs, axles, and u-joints can become weak and possibly break. Therefore, this leads to transmission problems and even possible transfer case replacement, which is not cheap. Only Full - Time 4WD can create equal balance of power between the front and rear tires, which is where the center differential comes into play.

[msdz]

IF you are having your front wheels spinning faster than your rear wheels then the gearing in the differential is OFF, that doesn't have nothing to do with the transfer case. Transfer case distributes a 1:1 ratio, if it doesn't then somebody has/had switched it from what it should be. That is also the reason why they always claim to run the same size tires of the same brand and never swap new tires with old ones, to avoid the faster wheel spin either from the front or the rear. A person that may set up a a mud buggy and strickly a mud buggy will have the gears higher in the front so the front helps pull them through the mud better though.

[sreilly77]

Originally Posted by msdz

IF you are having your front wheels spinning faster than your rear wheels then the gearing in the differential is OFF, that doesn't have nothing to do with the transfer case. Transfer case distributes a 1:1 ratio, if it doesn't then somebody has/had switched it from what it should be. That is also the reason why they always claim to run the same size tires of the same brand and never swap new tires with old ones, to avoid the faster wheel spin either from the front or the rear. A person that may set up a a mud buggy and strickly a mud buggy will have the gears higher in the front so the front helps pull them through the mud better though.

Your front wheels spin faster when you turn...In part time 4WD the transfer case locks and all tires are force to spin at the same RPMS. In full-time 4WD the tires can spin easily at any RPM via the center differential

http://www.jeepforum.com/forum/showthread.php?t=125373

Check out the link above. This will explain to you everything you want to know.

[msdz]

Originally Posted by sreilly77

Your front wheels spin faster when you turn...In part time 4WD the transfer case locks and all tires are force to spin at the same RPMS

I understand about the tires spinning faster on the outside wheels as your making turns, I thought you were stating the front wheels constantly spun faster than the rear, my mistake.

But still, I have done enough work on transfer cases to see they are to simple for what everybody is claiming, they do not lock causing power to all four wheels or are any of them that different except for the way they may engage, either by a a little electric button or by a manual selector. It is the diffs that determine whether or not all four wheels are going to have power. People are making the transfer case sound sooo complex and it is really a very simple set up. As I said before, some vehicles may have a set up for the part time to engage a diff lock for all 4 wheels to have power. Not all vehicles with part time is going to have that though.
I am still going to look farther into the locking diffs as being the "difference between part time and full time 4x4".

[sreilly77]

Originally Posted by msdz

I understand about the tires spinning faster on the outside wheels as your making turns, I thought you were stating the front wheels constantly spun faster than the rear, my mistake.

But still, I have done enough work on transfer cases to see they are to simple for what everybody is claiming, they do not lock causing power to all four wheels or are any of them that different except for the way they may engage, either by a a little electric button or by a manual selector. It is the diffs that determine whether or not all four wheels are going to have power. People are making the transfer case sound sooo complex and it is really a very simple set up. As I said before, some vehicles may have a set up for the part time to engage a diff lock for all 4 wheels to have power. Not all vehicles with part time is going to have that though.
I am still going to look farther into the locking diffs as being the "difference between part time and full time 4x4".

Well I took apart the transfer case on my Jeep before and it is a very simple set up. What you are saying about leaving the vehicle in part-time 4WD on dry surfaces is starting to make sense to me. The only thing that gets me is these forces that people are saying from the front drive shaft against the front differential. What I'm wondering now is where does the center differntial comes into play with the Part-Time and Full-Time 4WD, like what is the difference if the diffs do lock? I know that there is no way there are locking diffs on my Jeep. If there were I would have seen all four wheels spinning when I was trying to pull someone out of the mud in full time and then part time and it was basically the same results: one wheel spinning in the front and one in the rear, sometimes 2. Even when the manual says part-time is for basically off road conditions, I have driven the Jeep in Part-time 4WD today and made a turn with it on and didn't have any problems with understeer. So I agree with you on the fact that we need more info when it comes to the differences between Full-Time and Part-Time 4WD. So then the question remains: WHAT IS THE DIFFERENCE?

[msdz]

If a person has a "locking" differential there is no difference in driving as long as the vehicle remains straight. If you were to turn your steering wheel either direction with a "locked" differential in the front axle the outside wheel needs to turn faster to have good steering without force being applied to the axle, the outside wheel travels a farther distance to become straight again. The inside wheel of course spins slower and goes less distance. With the wheels being forced to spin at the same speed with a "locked" differential it causes strain on the tires and axles, on hard surface the outside wheel is usually going to squeal unless it has the better traction then the inside will. Also the tires will wear or if the traction is really good with the tires then the axle will snap.

My definition of:
Full-time or AWD: no driver input required to have 4WD, meaning no worries about the wife making a poor judgement and not putting it in 4WD when needed or putting it in 4WD when not needed.

Part time: driver input is required to lock transfer case in and/or turn manual hubs in. Meaning better MPG and less wear on all moving parts. Also means wife will most likely be running 4WD when it is dry and sunny or be in a ditch cause she thought it was already in or didn't think she needed 4WD.
Possibly with this thought as well, part time 4WD might "lock" the differential together with vacuum lines or electronically controlled solenoid for a truer 4WD.