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Going into 4LOW will put you in Part-Time 4WD, or 4x4. The front and rear axles will turn at the same speed. You can not use this mode on high traction surfaces, it has to be a low traction surface that allows the tires to slip. Because as you turn, the wheels will slip on the surface.

So, you want to avoid trenching the yard. So keep in mind how 4LOW works. the low gearing might avoid wheel spinning and thus the trenching. At the same time, if you turn, wheels are going to slip and the slipping could do yard damage and it might get trenching started.
 

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Ok, the MP3023 does not have a center differential, it has a wet clutch pack, the rear drivetrain is directly driven no differential, gearing or disconnection, other than the reduction planetary gear, which would directly drive the rear output just at a different ratio. The front drivetrain is connected to the rear drivetrain output by a chain and the wet clutchpack that is computer controlled to increase or decrease pressure to allow more or less slip or disengage the front drivetrain completely.

So, in a way it acts like a center differential, but not really in the true sense, in the final affect, yea its the same....

Full Time 4WD means the 4WD can be used in all conditions, i.e. it can be in 4WD full time.
Part Time 4WD means the 4WD can NOT be used in all conditions, i.e. it can only be in 4WD part time.

As Driveabout mentioned, the industry has turned all these terms into marketing terms, meaning the manufacturer just calls anything they want by these terms, no matter how fast and loose they are playing with the definitions. As well, Jeep has dropped these terms, you can't find them in the Grand Cherokee O.M. but earlier versions of the JGC or other models you'd find these terms all the time.

Previous Jeeps have had transfer cases that had a center differential and that would be Full Time 4WD and Jeep called it that in the O.M. It could also lock the center differential that would make it Part Time 4WD, and they called it that in the O.M.

The Jeep Wrangler has always had very tough and rugged 4x4, Part Time 4WD transfer case. It has no differential, nothing to lock. You simply engaged or disengaged the front drivetrain to choose between Part Time 4WD or RWD only.

So, in the WK2,

When you are in the default, you are in "Automatic 4WD" mode. Where the computer is allowing the front drivetrain to slip or disengages completely to make it RWD as necessary.

When you shift into 4LOW, the computer puts maximum pressure on the wet clutch pack to engage the front drivetrain and effectively locks the front drivetrain to the rear drivetrain. The O.M. does describe the front and rear drivetrains locking together. This mode is NOT for high traction surfaces, trying to turn on pavement can cause drivetrain binding or damage. It is for low traction surfaces that will allow the wheels to slip, because they will slip when you turn. This has been called Part Time 4WD for decades, Jeep just doesn't call this Part Time 4WD anymore.

In SHORT: Shifting into 4 LOW does change the system to Part Time 4WD mode, even though Jeep doesn't use the term, it meets the definition of the term.

Note: I can not find anywhere in the O.M. warning not to use 4 LOW on high traction surfaces. Pure speculation, but it may be the computer is reducing pressure on the clutch pack if it senses you turning, to allow some slip of the clutch pack and thus you wouldn't encounter drivetrain binding or damage. But that is a pure guess, I would not risk very expensive damage putting your WK2 in 4 LOW on dry pavement and then turning on the drive pavement. When I have used 4 LOW off-road I did notice the tires weren't slipping while making tight turns, which I expected, it could simply be I didn't sense the tires slipping and they were, it might be the computer might loosing up the wet clutch pack to prevent wheels slipping.
 

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JGC center differential exists and is "open", so it fits the definition of Full Time 4WD/AWD as you noted, DriveAbout. That's why it's so flexible in various conditions...it can be a nice, gentle "AWD" type experience on the highway while offering advanced tricks and capabilities in more difficult situations with QT-II/QD--II. I really appreciate how it was engineered in that respect.
The MP2010 transfer case of the QTI has a center differential, it also has no 4 LOW option either.
The MP3023 transfer case of the QTII and QDII has no differential at all, it uses a wet clutch pack, it does have a 4 LOW option.

It does fit the definition of Full Time 4WD (mostly) if you are in the Auto/Default mode, it can go to RWD for some periods when 4WD is unnecessarily which arguably does not make it Full Time 4WD, but perhaps not wrong to call it Full Time 4WD, since it will seamlessly go back to 4WD when necessary.

Even though the O.M. doesn't mention it, the description of 4 LOW meets the definition of Part Time 4WD.
 

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I remain in disagreement with your logic, Mongo. A 4x4 JGC is 4WD/AWD all the time. There is no method to make it 2WD, outside of disconnecting something physically. 4LOW is the most "4WD" it gets, even based on your description. But no matter...it's not really relevant to the OP's question.
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You can disagree with the logic all you want. But then you usually then double down and disagree with the data. You then refuse to explain how it works, claim you're not a car guy, so you're just going to believe what you want despite the data and references saying its not true.

I showed you load leveling does redistribute load, a youtube video with engineers actually measure the load on the axles showing the load distribution changed as the vehicle leveled. That is not to say that it is anywhere close to the what a weight distribution hitch can do, and load level can actually re-distribute load negatively. But actual measurements right in front of you and you continued to insist that load leveling can't change weight distribution at all.

The FSM, the industry literature about the MP3023 transfer case, and one of our members using AlfaOBD to monitor the clutch pack in the transfer case, all say that in Auto 4WD mode, the transfer case can and does go to RWD. Disagree with the logic all you want Jim, show me your DATA!

Now yes, Jeep does NOT give you an option to select RWD only, the MP3023 Transfer case is totally capable of doing this, and other vehicles that use this case do have the option to select RWD only mode. But the Transfer case also has a 4 HI mode, that Jeep does not use either, that mode puts into constant 4WD. Jeep uses the Auto 4WD mode by default, that varies front drivetrain engagement, to include going to RWD. So yes, you can't put the vehicle into RWD only, but by default, you're in Auto 4WD mode and while you're driving around on the street you in RWD a good amount of time, if not more than half the time.

The OP (my emphasis added):
...In past years when I've used either my old Bravada or more recently my brother's truck, we occasionally had trouble spinning and trenched the yard a bit. So I was thinking that if I dropped into 4Low to lower the gear ratio, there'd be a little less chance of that. Question is, is the gearing in 4Low ok for the extra load like that?

Side question, would using Sand or Mud mode further decrease the risk of trenching it?...
Seems the OP referred to trenching his yard more than once.
Like I explained, 4 LOW meeting the definition of Part Time 4WD may cause his wheels to slip as he turns, and a slipping wheel on the lawn could get into trenching, it may not or the advantage of the low ratio might overcome the disadvantage of the wheels slipping a bit. But it was something to watch out for and RELEVANT to the OP's question since he mentioned trenching his yard twice.
 

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A quick review of the 2011 FSM states the MP3023 in auto 4WD mode, the default, it provides on-demand 4WD, it does not specifically state that it goes to RWD according to conditions. But what does 4WD on demand mean? Sounds like to me, you get 4WD when you need, but why would it be on demand if it is constantly in 4WD? But I will grant you it might mean something else, but they do not explain what it means.

More than one piece of Industry Literature on the MP3023, remember it used in GM vehicle as well, if not more. Clearly states in Auto 4WD mode it can go back and fourth between 4WD and RWD as necessary.

The MP3023 can be switched between 5 modes, 4 HI, 4 LOW, Auto 4WD, RWD and Neutral.
This is done electrically with a switch/s.
Many of the other manufacturers that use this transfer case, make all 5 modes available with a selector switch or several switches.
Jeep elects to simply put the transfer case in Auto 4WD mode by default, with two separate switches to switch to 4 LOW mode or Neutral mode.
The industry literature describes 4 HI, as full time 4WD, in this mode it is constantly in 4WD at the higher ratio. The Auto 4WD mode actually varies torque biases and torque splits (only while the clutch pack is slipping) to include zero pressure on the clutch pack, which is RWD. Why would they have a 4 HI and Auto 4WD mode if they are the same?
 

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Again, if you have the ability to shift into 4 LOW, you have the MP3023 Transfer Case and it has no differential, open or otherwise.

It has a clutch pack that is computer control to allow slip, a little or a lot or total slip. In 4 LOW, it will it will increase the pressure on the clutch pack to lock the front and rear drivetrains, the O.M. says exactly that.

It is possible, despite the O.M. describing 4 LOW locking front/rear drivetrains, that when it senses the vehicle is turning, it eases up the clutch pressure just enough to allow the clutch to slip enough so the wheels won't slip. That would explain why they dropped the warning in the O.M. that has always been there for locking the front/rear drivetrains together, why I haven't seen any signs of wheels slipping in tight turns off-road in 4 LOW, and why MacDaddy has made turns on dry pavement in 4 LOW and not encounter drivetrain binding.
 

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Vertebrate White Product Organ Natural environment

1 - HOUDINI RETAINING RING
2 - INPUT BALL BEARING
3 - RETAINING RING
4 - CARRIER LOCK PLATE
5 - FRONT CARRIER THRUST WASHER
6 - INPUT GEAR ASSEMBLY
7 - CARRIER THRUST SHIM
8 - PLANETARY CARRIER ASSEMBLY
9 - RANGE SLEEVE
10 - MAINSHAFT ASSEMBLY
11 - OIL PUMP ASSEMBLY
12 - REAR THRUST WASHER
13 - REAR WEAR SLEEVE
14 - REAR OUTPUT FLANGE
15 - O-RING SEAL
16 - FLANGE NUT
17 - SCREW
18 - SHIFT MOTOR
19 - WORM SHAFT OIL SEAL
20 - RETAINING RING
21 - RETAINING RING
22 - BALL BEARING
23 - WORM SHAFT
24 - SHIFT RAIL
25 - RANGE FORK PAD
26 -RANGE FORK
27 - SLEEVE WASHER
28 - SPRING
29 - BRACKET ASSEMBLY
30 - RETAINING RING
31 - BARREL CAM
32 - SHIFT SHAFT ASSEMBLY
33 - BUSHING
34 - CLUTCH CAM
35 - GEAR
36 - COUPLING
37 - RETAINING RING
38 - BEARING
39 - REAR CASE HALF ASSEMBLY
40 - BOLT
41 - SCREW
42 - RADIAL SEAL RING
43 - SENSOR
44 - SCREW
45 - RETAINING RING
46 - SCREW
47 - IDENTIFICATION TAG
48 - FILL/DRAIN PLUG
49 - REAR BEARING
50 - SHIFT SHAFT BEARING RETAINING RING
51 - SHIFT SHAFT BEARING
52 - TUBE & SCREEN ASSEMBLY
53 - O-RING SEAL
54 - MAGNET
55 - SCREW
56 - SPRING
57 - DETENT POPPET
58 - CHAIN
59 - SPROCKET
60 - RETAINING RING
61 - FRONT BEARING
62 - FRONT CASE HALF ASSEMBLY
63 - DOWEL BUSHING
64 - RADIAL SEAL RING
65 - FRONT WEAR SLEEVE
66 - FRONT OUTPUT FLANGE
67 -RETAINING RING

Font Drawing Parallel Cylinder Diagram
 

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I did learn something I had always suspected might be true. That even in 4 LOW, the system is easing up the clutch for turns so wheels don't slip or bind. It's pretty sad that you can read the O.M. and all the Jeep literature and not get one clue how their equipment actually works. You left with hearsay and guessing.

For the O,P. that means what I mentioned about 4 LOW might start trenching if you're turning, that is less likely, but it can still happen in 4 LOW, you just have to watch out for it.
 

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Yep, @Mongo53 like I said between the open diff’s the clutch packs and the torque distribution WK2’s are one of the easiest user friendly and proven systems on the market. For the everyday driver to advanced off roader, Jeep rocks. They still need to go back to a complete live axle suspension front and rear with some high pinion 60’s front and rear, boy oh boy now we’re talking.
Those days are gone.... ....be thankful Jeep remained dedicated to true off-roading enough that kept the Jeep Wrangler true to the vision. Media, Lawsuits, Gov Regulation, Consumer Ignorance, Industry Trends, even crappy dealerships overcharging customers for repairs all work against live axles. Fact is, 98% of consumers have no idea what live axles are and don't care, they buy a Jeep because its not like other cars and then spend the entire time of ownership bitching why aren't they like other cars. They won't maintain or repair their suspension, and when they get death wobble they will scream Jeep makes defective vehicles its not their fault they haven't done one single thing for maintenance and repair, and then balk at the huge bill for all the work they have been ignoring for years. Gov Regs for roll over, lawsuits for rollover and death wobble, media printing articles panning Jeep is stuck in the 1950's still producing vehicles with live axles in this day and age.
 

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Here is the real world test. In 4 high the transfer case will stop sending power to the front wheels when the steering wheel is turned. In 4 low this behavior does not happen. All these tests were done in AUTO mode.

This is the steering angle as reported by AlfaOBD when its straight

This is the steering angle when the wheel is turned

Here is a video I made showing how the transfer case stops sending power as steering angle is increased.

Here is a video doing the same thing but in 4-low. Notice there is no change in the power applied to the clutches no matter what position the steering wheel is in.

You'll notice there is no change in transfer case clutch lock torque in 4-low meaning that steering angle has no affect when in 4-low.

Other food for thought. If you wanted to figure out torque split. Assuming 1710nm is fully locked meaning 50/50 F/R The system always transitions from RWD back to some fwd bias when at low speeds and at a stop. The T-Case Clutch lock torque is usually around 500nm or so. Meaning when taking off from a stop the QDII system has a power split of approximately 30F/70R under normal circumstances (no slipping or WOT throttle).

Since you now know how the torque split works in reality (not just what a manual says) you can watch this video and see how at low speeds and when taking off from a stop there is that 30/70 split and how most of the time the vehicle is in RWD mode.
Now I'm confused, I can see my own experience is just I missing the wheels slipping off road in 4 LOW. But MacDaddy swears he's driven on dry pavement in 4 LOW, turning with no binding or difficulties. Something wrong with his transfer case?

This is interesting! So let's say I was off-roading in my QT2 WK2, and I shredded a front CV joint. I could just pull fuse F77 and be able to drive my car home in RWD?
The MP3023 Transfer Case directly drives the rear drivetrain, there is no differential between the rear output and main shaft. The Clutch Pack is just engaging to transfer power to the front drivetrain. So no matter what happens to the front drivetrain, you will have power to the rear wheels, whether pull a fuse or not. Of course things wrong with the front drivetrain could cause more damage to the front drivetrain as you drive. So totally circumstances dependent on if you can drive or not with certain drivetrain failures, BUT, the rear wheels will always be driven regardless (unless of course the failure is the transfer case to the rear output).

What are the physical ramifications for running this way? I cannot imagine Jeep intended for this to be a way to use the vehicle.
Jeep did not design the MP3023 transfer case, Magna Powertrain did. Magna Powertrain designed the Transfer Case to run RWD. But it needs a discrete signal on one circuit at a specific voltage to set RWD mode. Pulling the fuse might not provide that, as well for all modes besides RWD, the computer has to actively manage the clutch pack, RWD mode simply provides zero pressure to the clutch pack. So in theory, as long as you have no pressure on the clutch pack you are in RWD mode, of course in practice can be different. Someone is going to have to risk it and see, if we are to ever get the answer.

Here's what my 2014 owners manual, latest revision I have, says about when you should not use 4WD LO... it's for loose, slippery road surfaces only.

View attachment 238684
I searched my 2011 O.M., there is nothing about this at all in the 2011 O.M. It does say 4 LOW does lock front and rear driveshafts together. Nothing about on for loose surfaces or NOT use on dry pavement, etc.....
 
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