NV245 Transfercase Operation - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 37 (permalink) Old 05-31-2011, 07:10 AM Thread Starter
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NV245 Transfercase Operation

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?

06 Red Jeep Commander 3.7L V6 "Manual QT2", RC 2" w/ Rusty's 1/4", 1-1/4" Wheel Spacers, Rubicon Moab Wheels, Grabber AT2 LT265/70-17 tires, Rocky Road Supersliders, Fastman Throttle-body, K&N Cold Air Filter, JBA Shorty Headers, Front Tow Hooks, 2" towing receiver front & rear, Wired for winch front & rear, ARB Onboard Air, Trans Temp Gauge, Aux Trans Cooler, Sport Roof Crossbars, Skid Plates, RS5010 Rear Shocks, JKS 2034 Front & 2001 Rear Disconnects

Last edited by cmdr jim; 05-31-2011 at 07:23 AM.
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post #2 of 37 (permalink) Old 05-31-2011, 07:55 AM
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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)

-Matt
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post #3 of 37 (permalink) Old 05-31-2011, 07:59 AM
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And are you sure they're not just transition points that aren't actually used in "drive" ?

-Matt
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post #4 of 37 (permalink) Old 05-31-2011, 08:49 AM
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Quote:
Originally Posted by Matt_ View Post
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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post #5 of 37 (permalink) Old 05-31-2011, 09:10 AM Thread Starter
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Quote:
Originally Posted by Mongo View Post
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.

06 Red Jeep Commander 3.7L V6 "Manual QT2", RC 2" w/ Rusty's 1/4", 1-1/4" Wheel Spacers, Rubicon Moab Wheels, Grabber AT2 LT265/70-17 tires, Rocky Road Supersliders, Fastman Throttle-body, K&N Cold Air Filter, JBA Shorty Headers, Front Tow Hooks, 2" towing receiver front & rear, Wired for winch front & rear, ARB Onboard Air, Trans Temp Gauge, Aux Trans Cooler, Sport Roof Crossbars, Skid Plates, RS5010 Rear Shocks, JKS 2034 Front & 2001 Rear Disconnects

Last edited by cmdr jim; 05-31-2011 at 09:15 AM.
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post #6 of 37 (permalink) Old 05-31-2011, 09:26 AM
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Quote:
Originally Posted by cmdr jim View Post
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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post #7 of 37 (permalink) Old 05-31-2011, 09:28 AM
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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.

-Matt
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post #8 of 37 (permalink) Old 05-31-2011, 09:40 AM Thread Starter
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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.

06 Red Jeep Commander 3.7L V6 "Manual QT2", RC 2" w/ Rusty's 1/4", 1-1/4" Wheel Spacers, Rubicon Moab Wheels, Grabber AT2 LT265/70-17 tires, Rocky Road Supersliders, Fastman Throttle-body, K&N Cold Air Filter, JBA Shorty Headers, Front Tow Hooks, 2" towing receiver front & rear, Wired for winch front & rear, ARB Onboard Air, Trans Temp Gauge, Aux Trans Cooler, Sport Roof Crossbars, Skid Plates, RS5010 Rear Shocks, JKS 2034 Front & 2001 Rear Disconnects
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post #9 of 37 (permalink) Old 05-31-2011, 10:15 AM
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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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post #10 of 37 (permalink) Old 05-31-2011, 10:41 AM
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48\52 split in AWD until wheel slip is detected the TC locks to 50\50. 4LO TC locks 50\50 thats it. This comes from the jeep engineer him self so I'm hoping he knows what he's talking about.


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