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Discussion Starter #1 (Edited)
I have a NV245 transfercase sitting on my workbench. I have an extra transfercase motor as well. So I took apart the extra transfercase motor. It has four sections:
The motor part of it is a simple DC brush type motor with a gear attached to the end of it's shaft. The gear also has a hex shaped section.
The second section is a solenoid, springs and three metal disks. The center hole of the middle disk being hex shaped to match the hex on the motor shaft.
The third section is three sets of planetary gears, a speed reduction.
The four is a rotary sensor, simpular to a rotary potentiometer​

I put the disassembled motor on the NV245 transfercase with just the planetary gears and shifted the transfercase through it's entire range of motion. What I found out is there is really an "open" 4HI, a limited slip transition to "Locked" 4HI, (If it wasn't for the solenoid and the hexes, the clutches can back drive the shifter shaft in locked 4HI). Neutral in the center, and then an "open" 4LO, a limited slip transition to "Locked" 4LO (and again the solenoid must lock the transfercase in position or locked 4LO wouldn't stay).

So here is the question for you guys with QTII or QDII, you get some tire spin from front to rear axles in 4LO for a very short time before all axles turn the same speed? Is Jeep using the open and limited slip section of 4LO or do they go right to locked?
 

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There's no slippage front/rear that I've ever noticed.

I'd venture to say that the "open" modes are activated under certain conditions.... like highway driving or low speed tight turns. Or it could be similar to how the ELSD activates so quick that its almost discernable (in forward anyways)
 

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I'd venture to say that the "open" modes are activated under certain conditions.... like highway driving or low speed tight turns. Or it could be similar to how the ELSD activates so quick that its almost discernable (in forward anyways)
My pure guess, would be it would be like that, but biased more toward always being an open diff, with ELSD limiting and locking come on if it senses slipping.

How does the vehicle know you are doing highway driving, other than speed? Open diffs distribute power pretty well all the way up to when you start to loose traction then they loose it. While limited slip can cause you to loose traction on wet roads or tight turns.

Just guessing, but it seems to me, it would keep the diffs open, especially center diff, you have the brake's ABS reacting to limit slip as well, until it recognizes the slip then start tightening them up or locking them.
 

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Discussion Starter #5 (Edited)
My pure guess, would be it would be like that, but biased more toward always being an open diff, with ELSD limiting and locking come on if it senses slipping.

How does the vehicle know you are doing highway driving, other than speed? Open diffs distribute power pretty well all the way up to when you start to loose traction then they loose it. While limited slip can cause you to loose traction on wet roads or tight turns.

Just guessing, but it seems to me, it would keep the diffs open, especially center diff, you have the brake's ABS reacting to limit slip as well, until it recognizes the slip then start tightening them up or locking them.
This is my thought as well. Open all the time at least in HI, but what about LO, do you think they use the open at all or just go to fully locked?
And fully locked here is just maximum clutch hold, not a true locking device.
 

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This is my thought as well. Open all the time at least in HI, but what about LO, do you think they use the open at all or just go to fully locked?
And fully locked here is just maximum clutch hold, not a true locking device.
I have the QT1, but from the posts I've read, when you go into 4LOW, it locks the differential. I'm trying to remember if I read that in the O.M. or its informed speculation on the board? When I read through all the EBCS and ESP system and posted about it, I think that is what the O.M. said for going into 4Low about locking the diff and then using the EBCS features for the other wheels. But, I could be remembering wrong.

Yes, I believe the NV245 has a set of clutches and uses the clutches to lock the differential. BUT, thats from what I've read and what appears to be the case from a couple of cut-away picks I've seen. Take it with a grain of salt.
 

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A lot of true [controllable] lockers actually use clutch packs. Clutches with enough force are very strong.

And good point... I can see them being bias towards open.

But as for "How will it know if you're on the highway"... simple, a combination of wheel speed, engine load and RPM. If you're in an offroading situation and getting the tires spinning over 30mph, there's bound to be wheel slippage/ variable rpms / and variable engine loads.

In either case its just conjecture.... but the system could work either way.

Not sure why there would be an open mode for Lo though... even the Jeep website states that the tcase locks when shifted into Lo.... maybe its a fail safe mode if there's sensor faults or damage? Like if the trans goes into limp mode while you're in 4lo, it would make sense to shift to "open" 4lo to reduce strain.
 

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Discussion Starter #8
With the electronic controls to these Jeeps it seems there are a lot of options Jeep has at it's use. I agree from reading the jeep description it goes directly into 4LO Lock. But the electronics allow Jeep to change that all.

It's like when machine design went away from cams, gears and relays to servo motors and PLCs. The options become almost limitless. That is where we are with cars and trucks, but it also takes away from the average person being able to make changes to there vehicle............ Or does it open up opportunities? I am starting to visualize devises for gear changes and for controlling the NV245 transfercase, despite the electronics on our Jeeps.
 

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Well you have more off road experience than I, but if your going into 4LOW, why would you want the center diff to be open? I can only imagine 4LOW always being a lock the center diff situation.
 

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Discussion Starter #11
Well you have more off road experience than I, but if your going into 4LOW, why would you want the center diff to be open? I can only imagine 4LOW always being a lock the center diff situation.
The only time I ever used LO unlocked was with my old Dodge Ramcharger it was full time 4wd, it had HI, HI Lock, LO and LO Lock. I lived in the midwest close to some Corp of Engineer lakes where the boat ramps are long and steep. It was great to use LO on those ramps putting a boat in.
 

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Discussion Starter #12
Out of the Service Manual, I think it answers the question about LO:

The NV245 transfer case provides Full-Time Active Four-Wheel Drive for optimum traction in a wide range of conditions and is used in Quadra-TracT II and Quadra-DriveT II systems. The transfer case center differential distributes torque 48 percent to the front axle and 52 percent to the rear axle along with an electronically controlled clutch pack that is coupled to the center differential for torque biasing. The NV245 electronics provide an active system because it can anticipate and prevent slip. The transfer case can redistribute 100 percent of torque to the front or rear axle, depending on need. For added traction when traversing steep grades, rough terrain or extremely slippery/poor traction surfaces at low speeds, the transfer case can be switched into 4WD Low, which multiplies engine torque 2.72 times and locks the clutch pack for maximum traction at all times. The Neutral mode allows the vehicle to be flat towed behind another vehicle. Electric shifting is accomplished with a T-handle transfer case lever in the shifter assembly to provide simplified operation and positive engagement of 4 Low. A pushpin button is provided to shifting the transfer case into Neutral
 

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The only time I ever used LO unlocked was with my old Dodge Ramcharger it was full time 4wd, it had HI, HI Lock, LO and LO Lock. I lived in the midwest close to some Corp of Engineer lakes where the boat ramps are long and steep. It was great to use LO on those ramps putting a boat in.
Yep, I can see that being an actual application people use, although rare for most people, I can see how once you have that ability, you don't want to give it up and want it on your next vehicle.
 

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Discussion Starter #14 (Edited)
The insides of a Transfercase Motor/Sensor:

At the top, 12Vdc Brush Reversing Motor
At the bottom of the motor armature is the 12Vdc Locking Solenoid w/ clutch plates
Next is 3 sets of planetary gears,
And under the gearing is a 3 wire rotary position sensor.

Controllable outside of the FDCM? I think so. Possibly another route to add a QT2 tcase to any QT1.
Would anyone be interested in a black box to do this?
 

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I would be very interested if it meant I could be closer to having QT-II!
 

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Discussion Starter #16
Bench test transfer case control.

Just using 12vdc to drive the motor, I have repeatable High Loc and Low Loc Positions.
I also have a very repeatable Neutral position, only problem is I'm shooting for High Position when I get Neutral.
Which tells me the response time to shut the motor off and de-energize the brake, is not fast enough at 12vdc motor speeds.
I need to pick up a PWM and reduce the motor speed and all should come into play.
 

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Discussion Starter #17
I have all 5 positions! High Loc, High, Neutral, Low & Low Loc, without the PWM. Now to test for repeatability.
 

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I have QTII, but am finding this very interesting. I am quite sure that electronics does play a role in the performance of 4WD in todays "fly by wire" technology. Please let us know...
 

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Discussion Starter #19
I have QTII, but am finding this very interesting. I am quite sure that electronics does play a role in the performance of 4WD in todays "fly by wire" technology. Please let us know...
There are a lot of good aspects of having the electronics playing a role in our newer Jeeps, traction control, stability control, anti-lock brakes, engine controls etc. The problems come to those of us who what to modify our Jeeps. Mine came with the QT1 transfercase and yes I could easily sell it and move up to a QDII equipped XK, but that's not what I was wanting to do.

When finished I will have a very capable v6 equipped Jeep XK. I will have all the great features of QT1 on the road, traction control, etc. But off road, I will end up with full manual control of my transfercase and my front and rear lockers. If not for the way the NV245 transfercases operate, a simple manual lever shifter would have given the same results I'm looking for. And what I thought was the easiest part of all this (lower gears 3.55s) have become the most difficult to achieve. Without the support from Jeep or the aftermarket, we may never be able to lower our gear ratios.
 

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Hi Jim,

I have QT2, would you be able to put something together that would allow for stock operation or the selection of 4HI locked, 4HI unlocked, 4LO Locked, 4LO Unlocked. similar to the attached diagram....

Would you be able and willing to offer something along those lines or provide a schematic so we could build our own??????
 

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