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Please Explain Freedom Drive?

Discussion in 'Compacts: Renegade, Patriot, Compass, Caliber' started by Rick Anderson, Jan 13, 2017.

  1. Rick Anderson

    Rick Anderson Well-Known Member

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    My Daughter just got a low mile 2015 Jeep Compass, 4WD I believe it has the 2.4L and 6spd Automatic and 4WD.

    It has a 4WD Lock T lever. I advised her not to ever engage the 4 wheel lock on dry pavement. As best I understand it, it will lock the differential between the front/rear axles and make the system part time 4WD, i.e. 4X4; and all know what that means for turns on dry pavement.

    I can't seem to find much info on this Freedom Drive, its only marketing terms, dumb down stuff just making big claims. Some contradictory information, some saying its FWD and implying engaging the 4WD lock just engages the rear axle to make it full time 4WD. And then other sources claim its FWD or automatically switches to full time 4WD, and implies the 4WD lock mode changes it to part time 4WD.

    I looked at a PDF of the Owners Manual and there is no warning about 4WD Lock and not engaging it on dry pavement.

    So whats the deal?
    Does engaging 4WD Lock actually locks the center differential, make it part time 4WD and thus should never be driven on dry pavement in those conditions?
    Does the system switch back and forth between FWD and 4WD during normal driving? If it does, is it electronically controlled to do so with the ECC? Or is it merely a reaction from applying brakes to limit wheel slip, results in directing power to the rear axle.
    [​IMG]
    There is a Power Transfer unit attached to the starboard side of transmission output. It has at least a ring and pinion to a 2 segment driveshaft to an Electronic Controlled Coupling unit, then too the rear differential.

    So I guess, the key to understanding this, is just exactly does this rear electronically controlled coupling do?
     
  2. ImperialCrown

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    I'm sure that the owners manual would give a caution or warning if there was a potential for drivetrain damage.
    YouTube has a couple of videos that explain the FD1 and FD2 very nicely through animation:



     
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  3. Stratuscaster

    Stratuscaster Vaguely badass...
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    It's worth noting that the "automatic" in the Patriot when equipped with either FD I or FD II is the CVT2/CVT2L, and not a traditional 6-speed automatic. (Euro models allegedly can get a version of FD with the 6-speed manual.)

    The 4WD lock splits the torque 50/50 front/rear and the traction control handles moving power from side to side.

    I myself wouldn't lock the 4WD on dry pavement.
     
  4. ImperialCrown

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    Both the CVT2/L and Hyundai Powertech 6-sp automatic transaxle are described in the 2015 Compass manual. This changeover was a running change that year. The use of the 4WD-LOCK is described on p. 341.
    When to use the L range and 4WD LOCK begins on p. 343.
    http://cdn.dealereprocess.com/cdn/servicemanuals/jeep/2015-compass.pdf
    I agree that L and 4WD LOCK shouldn't be necessary on dry pavement during normal driving conditions and it may stress driveline components needlessly.
     
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  5. Stratuscaster

    Stratuscaster Vaguely badass...
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    Noted. For whatever reason I was under the impression that FD1 was not available with the Powertech - and I am now corrected.
     
  6. Rick Anderson

    Rick Anderson Well-Known Member

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    Keep in mind, my daughter is a state away, and she's not that technically inclined so I have to take what she says with a grain of salt, cause she could be wrong and I have not seen the vehicle yet.

    Yes, I've seen those videos, and they do fall into the category of dumb down, marketing terms. No where do I find any descriptions about differentials, clutch packs, solenoids are a basic principal of operation, simply a dumb description of the result. And the O.M. isn't any better.

    From what I've read, the Compass at least is now offering a 6spd automatic as well as the CVT.
    From what I can tell, the Freedom Drive I and II are the same system, its only FDII comes with a CVT2L (L for low) that the transmission is capable of going to such a low ratio, it creates the crawl mode for the system, not another gear set in the transfer case (or PTU or Coupler in this system). So FDII couldn't be available with the 6spd Transmission.

    I have NOT found if the Freedom Drive has a center differential yet. I have found some info I'll post below about the ECC (electronically controlled coupling) unit. Mitsubishi has an ECC as well in what looks like a similar 4WD system, and the timing does seem right this ECC might be shared technology from Chrysler's partnership with Mitsubishi.

    I have to agree, I really see no reason to engage the 4WD Lock on dry pavement. The advice I gave her was to only engage it if she gets stuck, then disengage it once she gets unstuck. If the drivetrain would bind during turning on dry pavement while in 4WD Lock, you would think the O.M. would warn of such a thing.
     
  7. Rick Anderson

    Rick Anderson Well-Known Member

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    Willie Racine's Jeep | New Jeep dealership in South Burlington, VT 05403

    The only difference I can find between FDI and FDII is the transmission that comes with FDII that can go down to a crawl ratio.

    Now the ECC, this is a Mitsubishi ECC, I could be wrong it might NOT be the same ECC in the Freedom Drive, but it appears to be the same. Perhaps its the other way around, Mitsu is using Chrysler technology.
    4-Wheel Drive | Technology Library | Automobile Technology | Mitsubishi Motors Automobile Manufacturing | MITSUBISHI MOTORS
    http://portal-diagnostov.ru/index.p...bishi-outlander-eng/32977-m227000070004900eng
    [​IMG]
    So, it appears the ECC can be disengaged to allow the no torque to the rear axle, partially engaged to allow partial torque to the rear axle or fully engaged to transmit all torque to the axle, which would be a 50/50 torque split. There is an explanation of the Pilot Cam and Ball how it applies pressure to the clutch pack based on relative motion, which is likely how a partial engagement results in partial torque.

    I found descriptions of the electronic control engaging the ECC, it is a pro-active control, not simply the Brake Traction reacting to slipping, although slipping wheels is an input to engage the ECC, relative wheel speeds, even throttle application (i.e. you stomp the gas pedal it knows you'll need more traction and engage the rear axle).

    The 4WD Lock appears to be just an override to the electronic control of the ECC, activate it and it keeps the ECC in the 100% lock mode.
     
  8. Stratuscaster

    Stratuscaster Vaguely badass...
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    The Patriot does as well - 5-speed manual, CVT2, CVT2/L, and Powertech 6-speed automatic.

    This is correct - FDII is ONLY available with the CVT2/L - that's what allows the FDII-equipped Patriot & Compass to carry a Trail Rated badge.

    From what I understand - and that's limited, admittedly - the LOCK only splits the torque front/back at keeps it at 50/50 - it's the traction control/braking that manages the power at the wheels/side-to-side - and perhaps that's what allows them to forgo the traditional "no 4WD lock on dry pavement" warning.
     
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  9. Rick Anderson

    Rick Anderson Well-Known Member

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    But the Power Transfer Unit? I can find nothing on the PTU or a center differential.
    [​IMG]
    Just by appearance I'm guessing there is no differential in the PTU, but I could be wrong, for a vehicle this size it might not need a very large differential.

    So this is the key, is there or isn't there a center differential in the system.

    If the PTU contains a center differential this makes a lot of sense, its a full time 4WD system that simply disengages/engages/partially engages the rear axle as necessary or demanded. Thus no worries about turning on drive pavement. And bare in mind, the brake traction system would limit wheel slip and loss of torque at slipping wheels, redirecting torque to wheels with traction. So the brake traction system creates virtual Limited Slip Differentials (LSD) at all 3 differentials. In this case, the 4WD Lock would not be a problem on dry pavement, since its just full time 4WD.

    But if the PTU doesn't contain a center differential, how would the system work? It would be a part time 4WD system, that would bind in turns on dry pavement. Unless the ECC could allow slippage during turning. The ESP has steering wheel sensors, yaw sensors, relative wheel speeds and tracks turning of the vehicle, so building into the system recognizing turning and the ECC responding by allowing slip for the turning would work the same as having a center differential. But, that still leaves open questions about 4WD Lock, if you engage 4WD lock, does the system ease up on the clutch pack to allow slippage during turns or does it NOT, thus you'd get binding in turns on dry pavement.

    Considering how there is nothing in the O.M. about not engaging 4WD Lock on dry pavement or NOT turning with with 4WD Lock engaged on dry pavement, its reasonable to expect that the system does something to avoid binding during turns on high traction surfaces.

    So that is the final question, does the PTU have a differential in it. If it does, that answers all my questions. If it does NOT have a differential, I can see how that works but I still have a few questions still.
     
  10. Rick Anderson

    Rick Anderson Well-Known Member

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    Yes, we have to guess from what little information has been given about the system. But, keep in mind:

    With a center differential, you can still have a 50/50 torque split, and be able to make turns on dry pavement.

    4WD Lock may mean, it simply locks the ECC into being fully engaged to provide the 50/50 torque split.

    or it could mean:

    If there is no center differential, and the ECC disengages or partially engages to allow slip, to act like a center differential. 4WD Lock could mean it fully engages, to act like a locked center diff, or simply part time 4WD. Again, they still have the ability in 4WD Lock to recognizing turning on dry pavement, and loosen up the ECC engagement to prevent binding, but no one knows if they do that.
     
  11. BobbiBigWheels

    BobbiBigWheels I'm likely at work...
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  12. Rick Anderson

    Rick Anderson Well-Known Member

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    Thanks, but it doesn't give details, like if there is a center differential or how the system allows different wheel speeds front/rear in turns.
     
  13. ImperialCrown

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    The 4WD system in the PM/MK vehicles looks similar to the past AWD minivans with the PTU (power transfer unit) outboard the right-side of the transaxle.
    It is a mostly durable and compact system, but with an added electronically-controlled clutch.
    The front/rear coupling is never 'rigid', but may favor rear torque transfer when wheel slip (from the ABS sensors) is detected.
     
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  14. Rick Anderson

    Rick Anderson Well-Known Member

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    I'd like to know for sure, and its darn shame manufacturers don't publish the information likely cause they believe their customers are uninterested and/or too stupid to understand it.

    I suspect the system is like you described, no center differential, everything needed for engage/disengage and allowing differential speed between front/rear axles is done with the electronically controlled clutch pack/coupling (ECC) at the front of the rear differential being driven by the driveshafts.

    I suspect that is why there is no warning in the O.M. about 4WD Lock when making turns on dry pavement. I "suspect" 4WD Lock, the same electronic control for normal mode, it recognizes when the vehicle is turning and loosens up the clutch enough to allow turning without binding.

    But, it would be nice to know for sure, instead of guessing from incomplete dumbed down information.
     
  15. ImperialCrown

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    I found this for the related Caliber AWD. Only Freedom drive has the driver-input 4WD LOCK lever, but the electronics, traction and turning strategy for the AWD system may be similar. ECC = Electronically-Controlled Coupling:

    [​IMG] Originally Posted by Service manual
    MODULE - FINAL DRIVE CONTROL

    DESCRIPTION


    The ECC is controlled by it’s own controller that is located in the left kick panel area. It gets signals over the CAN bus from the ABS Wheel speed sensors and TPS signal.

    OPERATION
    The all-wheel-drive system requires no driver input or control. Under most driving conditions, it is passive and power is transmitted to the front wheels alone. Unlike all-wheel drive systems that rely on pumps or viscous fluids to transfer torque, this system requires no front-to-rear slippage for activation. This allows the system to transfer torque solely in response to accelerator pedal position. If the driver is asking for a lot of power, the system immediately starts clamping the electronically controlled coupling (ECC), transferring a high percentage of power to the rear wheels.

    This avoids front wheel slippage, as power to propel the car is transmitted through all four tires. This mode of operation is called open-loop operation in that there is no feedback to affect the torque transfer. A second, closed loop, operating mode uses feedback from the wheel-speed sensors to determine the appropriate torque transfer. When the front wheels slip, the allwheel- drive electronic control module tells the ECC to start clamping, sending power to the rear wheels. Attempting the same aggressive launch described above with the front wheels on ice and the rear wheels on dry pavement, the ECC sends even more torque to the rear wheels to minimize slippage and launch the vehicle. Both modes are always active with the closed loop mode layered on top of open loop mode to increase torque to the rear wheels when needed to maintain traction in extreme cases.

    Power to the rear wheels is modulated under the following conditions:
    • Slipping on ice while backing up will send a lot of power to the rear axle
    • Loss of traction while traveling at freeway speeds, for example hydroplaning on a puddle of water, will send very little power to the rear wheels because the controller knows at those speeds a lot of power is not needed at the rear wheels.


    A third condition, which is independent of the others, uses wheel speed differences to determine when the vehicle is turning in a tight circle. This condition, which is indicated by a large
    discrepancy in side-to-side wheel speeds, causes the electronic control module to reduce torque to the rear wheels to prevent binding in the driveline. The electronic control module is always checking for this condition as well. A fourth condition that is unique to the Caliber system is to influence vehicle dynamics. Other manufacturers limit AWD to aiding traction or providing off-road capability. They concentrate on launching the vehicle or going off road at speeds up to about 25 mph (40 km/hr).

    Above that speed range, they use it to limit wheel slip for traction. On this system, additional ECM calibration controls torque to the rear wheels for improved handling in the 25-65 mph (40-105 km/hr) range. In this speed range, the system increases torque to the rear wheels during cornering with the throttle open to make the car turn more easily – make the handling more neutral. This is more readily accomplished with an electronically controlled system, than with viscous-coupling or gerotor systems that require some degree of front-to-rear slip to transfer torque to the rear wheels. Above 70 mph (113 km/hr), the control strategy provides minimal torque to the rear wheels under normal driving conditions to aid fuel economy. The ECC system is easier to calibrate, more flexible and more precise than viscouscoupling, Torsen, or gerotor system, but less costly. It is also less costly than the systems used in luxury cars from other manufacturers while providing similar functionality.

    The electronic control module also interfaces with the ESP and traction control systems. The interface allows the ESP system to use the ECC to help gain control of the vehicle. For this purpose, torque transmitted to the rear wheels by the ECC can be reduced. The Caliber AWD system is not traction control. It only works on situations where front-to-rear traction varies, for instance, front wheels on ice, rear wheels on dry pavement or climbing steep grades. AWD does not aid side-to-side traction. ESP does that through brake intervention on this system.
     
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  16. GLHS60

    GLHS60 Well-Known Member

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  17. Rick Anderson

    Rick Anderson Well-Known Member

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    So you're saying Jeep uses the same ECC as KIA? Which I had incorrect, assuming just by association and appearance from my searches it must be the Mitsubishi ECC that is fairly well explained. But principal of operation is fairly similar.

    Thanks, but again, there is a missing bit of info. How does the 4WD system handle differential wheel speed between front/rear axles with 4WD/AWD engaged?
    • Is there a differential in the PTU, or it just beveled ring and pinion?
    • Does the ECC simple disengage for any turning?
    • Does the ECC simply ease up to allow slippage during turning?
    • In 4WD Lock mode does it disengage/slip to prevent binding on high traction surfaces?
     
  18. ImperialCrown

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    I believe that Mitsubishi, Kia (Hyundai) and DaimlerChrysler all had a hand in developing the powertrain for the PM/MK vehicles. The WGE (world gas engine) was developed jointly and used by all 3 companies with their own tweaks.
    Looking underneath these vehicles on a lift, the chassis/undercarriage looks much like a Mitsubishi Galant. No coincidence here.
    There is likely a hypoid setup in the PTU to drive the rear axle. It is coupled by the ECC to transfer torque or not. If it doesn't totally disengage on sharp turns, I'm sure that it backs off engagement considerably. The PTU is serviced by unit replacement only. There are fluid change plugs provided.
    The electric '4WD LOCK' switch probably doesn't provide an absolutely solid clutch lock, but gives a more aggressive ECC engagement duty through software for more demanding traction conditions. Driving around town in 4WD LOCK would light the dash indicator and you may not notice much different behavior on dry turns and pavement maneuvers, because the ECC will back off for those conditions.
    I drove the Grand Cherokees with the NV249 that had the viscous coupling (front/rear) and they would 'crab-walk' on tight turns. Some felt like they were jumping sideways in parking lot turns. Replacing the internal coupling sometimes helped, but they all did it to some degree.
     
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  19. Rick Anderson

    Rick Anderson Well-Known Member

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    Thanks IC, that is what I guessed from what info I could find. Your experience helps confirm it more for me.

    The info I found on the Mitsibushi ECC said it was electromagnetic driving a pilot clutch and cam setup to apply pressure to the plates, while the link for the Kia ECC said it was an oil pump driven by an electric motor that applies pressure to the clutches. Regardless, they look very similar in every way except the force application to engage the clutch packs.

    The PTU being unserviceable also lends credence to it being nothing more than a Hypoid Gear setup to tap off power. If there was a differential, it likely would be serviceable, since at least a few of the differential parts would be easily serviceable. If its just a hypoid gear I can see it NOT being worth it to design it to be serviceable (Hypoid Gears needs precision setup and a major part of the design has to be invested in servicing it in the field with tools available to mechanics to do it properly). If the PTU is just the hypoid gear, they could set up an assembly process that is much faster and cheaper to precision align it, but didn't have the provisions to redo the setup in the field.

    Yea, I'm guessing the idea behind the 4WD lock is simply, when the driver knows he needs the rear axle engaged 100%, he can throw it and get better results than waiting for the electronic system to recognize and react to engage it.

    Probably in all modes, the system recognizes when the vehicle is turning and loosens up the ECC enough to allow the turn without binding.

    I've seen some speculation on forums (and it didn't seem to informed) that the 4WD Lock will turn itself off above a certain speed) so perhaps the 4WD Lock loosens up less for turns because it would off at higher speed turns.
     
  20. GLHS60

    GLHS60 Well-Known Member

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    I think you have it mostly figured out.

    No center diff, clutches are electrically/hydraulically engaged/disengaged instantly to provide
    FWD or AWD as needed.

    Lock is for situations like heavy snow where there could be lock/unlock hunting.

    I have experienced the lock/unlock hunting with G.M. Cuckoo clock, or Gov.Lock rear diffs. and assume that's what they want to avoid.

    F.D. II a rather ingenious way of providing low range using the CVT.

    Thanks
    Randy
     
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