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The 2018 Jeep Wrangler JL status thread

Discussion in 'Mopar / FCA News' started by 12soldier, Aug 8, 2015.

  1. Rick Anderson

    Rick Anderson Well-Known Member

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    They can change the transmission, the transfer case, the driveshaft and/or its u-joints OR the wheelbase.

    Changing the transmission is very limited unless FCA wants to spend a lot of money and take a lot of risk, its NOT like there is a lot of unused spaced inside the ZF 8spd.

    The transfer case is a possibility. You could compact it and make it shorter.

    The driveshaft, the shorter the driveshaft the greater the angle at the u-joints as the axle goes up and down.

    U-joints have a maximum angle they can go to, exceed it, they bind up and destroy themselves or the drivetrain. There are different types and they can go to different angles, each with their positives and negatives. The bigger the angle the higher the cost.

    A Wrangler has 4 times the suspension travel of a Charger, and the Wrangler is a solid axle, while the charger has independent rear suspension, i.e. the driveshaft doesn't have to move up and down.

    A Wrangler has a front solid axle with a lot of travel, it will have to clear the engine, so if you push the engine forward the front axle has to go forward, i.e. longer wheelbase.

    The 4 door variant already has a longer wheelbase, the ZF 8spd won't be a problem for it. The 2 door variant has a short enough wheelbase, the ZF 8spd will be a problem for it.

    IIRC, Bob's article ruled out changing the trans, just too expensive/impractical/big of a risk. Compacting the transfer case or increasing the wheelbase seemed the most likely options, then possibly different u-joints that can go to greater angles might be an option.

    A bigger engine compartment? Remember the JL is suppose to be smaller. The engine compartment likely isn't going to be larger, if they push the engine forward, they will push the firewall with it. Bob (or maybe someone else) spoke about a design principal that Jeep has always stuck by that the firewall is at the trans/engine mating within a set distance, for a whole bunch of reasons. So if they don't push the windshield forward, then there will be a longer hood or plug/panel between the windshield and hood. If the windshield on the JL is going to be more raked back for aerodynamics, then you can move the base of the windshield forward with the firewall/engine and keep the top of the windshield at the same point, thus producing a greater rake. Something you don't see on the Mules, since they modify JK bodies to put on the JL chassis, and instead stick a longer panel between the base of the windshield and the hood.
     
  2. WXman

    WXman Active Member

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    The NSG370 will continue on, since they've already got it and it's easy to carry it forward. That's my thinking.
     
  3. link3721

    link3721 Yes, This MK Goes Off-Road

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    IF that's the only manual to be had in the JL, I doubt they'll put it behind the diesel, or else it would have to be detuned. I'll take the diesel with auto over a detuned diesel with a manual.
     
  4. xjgary

    xjgary Well-Known Member

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    As Bob said, most built Wranglers use an aftermarket Slip Yoke Eliminator (SYE) kit to solve this problem without resorting to a major transmission modification. here is an example. JB Conversions, Inc.
     
    #1224 xjgary, Jun 1, 2016
    Last edited by a moderator: Jun 1, 2016
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  5. WXman

    WXman Active Member

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    I doubt the manual will ever be offered with the diesel. They didn't in '05+ Jeeps here in the U.S. And currently there are few to no small diesel 4x4s with a manual option in the U.S. It seems to be commonplace to do automatics only with the diesel option in the U.S. Probably because of emissions testing and durability.

    There's a big debate going on about whether Jeep will develop a new manual trans for JL and I don't see that happening. The manual trans. is a dying breed unfortunately. I think they'll keep the NSG370 for a while. I could be wrong.
     
  6. Ruptured Duck

    Ruptured Duck Active Member

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    True with the older Wranglers -TJ but the JK really does not require this. I have a 2dr with 4" lift and no need for an SYI kit.
     
  7. link3721

    link3721 Yes, This MK Goes Off-Road

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    They don't have to develop a new manual, they've got the Ram HD manual. But they'd still have to develop the connection to the engine. Getting the NSG370 hooked up to the Hurricane is probably easier/cheaper than getting the Ram manual hooked up to the diesel. So I guess I'll have to see if the diesel is enough of an upgrade to choose it over the Pentastar with a manual.
     
  8. Rick Anderson

    Rick Anderson Well-Known Member

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    Yea, I "thought" the JK does NOT have a slip yoke, it has a fixed yoke already at the XFR case. Its that way on my XK meaning its also that way on the WK. Correct me, if I'm wrong.

    The driveshaft looks different than the aftermarket driveshafts (at least on the XK/WK) used with SYE kits, but you can clearly see the driveshaft has two halves that are splined to allow it to elongate/collapse with geometry changes as it translates.

    I guess between a slip yoke and fixed yoke, at the most extreme angles, the fixed yoke driveshaft would be getting longer and thus reducing the extreme angle, thus it might get a few more degrees of articulation before hitting the critical point where the U-Joint could bind up.

    I do remember Bob saying that and NOT getting it. I thought possibly he was getting at using the Double Cardan Joint?, like a lot of those SYE kits use on the driveshaft, which I think can go to a much greater angles without binding. I'm really out of my element here, I may have some of this dreadfully wrong.
     
  9. Ruptured Duck

    Ruptured Duck Active Member

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    Here is a very simple image to explain what an SYE kit does. The bottom image is an OE slip yoke design. The "Slip" is located in the T-case side. Because of the short length of the drive shaft a well built Jeep with good articulation could extend the slip yoke far enough to pull it out of the t-case. The bonus when this happens is it allows your ATF fluid to flow out the back of your t-case. The slip shaft is your rear seal.

    The other tow images show the 2 types of kits on the market. the standard SYE kit eliminates the slip yoke and has a fixed seal. It also allows for a longer drive shaft and better angle. The top image shows whats called a Mega SYE. it nets even more drive shaft length and better angles.
    SYE.gif
     
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  10. Dr. Jeep

    Dr. Jeep Well-Known Member

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    You can solve this with a high pinion rear axle. The JK already moved the front axle from a low pinion design on the TJ to a high-pinion D44 or D30 on the JK. The pinion shaft was also enlarged.

    Additionally moving the rear axle to a high pinion design on the JL gives a better shaft angle to the Tcase output yoke as well as giving you higher clearance under the rear pinion, as well as better running clearance under the rear driveshaft. A high pinion design in the rear does bring up questions about the survivability of the ring gear vs. the low pinion design, but the internals can be beefed up and we already know they are refreshing these axles... so....

    ...a high pinion rear axle centersection gives you some negotiating room with a longer transmission.
     
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  11. Dr. Jeep

    Dr. Jeep Well-Known Member

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    For example, here is the difference between a low and high pinion front Dana 30 axle. I believe export XJ's used to get high pinion 30 fronts as I recall people importing the housings back in the day. Not until the JK did you see one stock in the front of a domestic Jeep. But you can see how the pinion output is several inches higher--and thus provides for much less severe angles with the tcase output. It could be done in the rear axle as well (the aftermarket already has a good number of high pinion D44 and D60 replacements for the JK rear axle).

    [​IMG]
     
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  12. CherokeeVision

    CherokeeVision Well-Known Member

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    XJ's used the high pinion D30 until toward the end when it became low pinion like the TJ.
    My 89 was high pinion but my 01 is low pinion.
     
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  13. Rick Anderson

    Rick Anderson Well-Known Member

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    Is that photo/diagram showing an OE rear driveshaft the current JK? If it is a current JK OE rear driveshaft than I was wrong, because that photo/diagram clearly shows a slip yoke as OE. Granted its different only in the fact it has an accordion rubber cover that is probably more effective at keeping out dirt and water than the old slip yoke seals.

    I think that was what bob was getting at talking about the SYE kits, that photo shows it clearly, while you don't get it in words. A good SYE kit, especially if you do it OE from the ground up and NOT an aftermarket bolt on kit that has to reuse the other design. Makes for a longer driveshaft in the same amount of space (because you don't need the room for the slip yoke to move in and out) and it uses the double cardan joint that goes to greater angles as well. You don't have to have a double cardan joint to make it a fixed yoke, the fixed yoke on the XK/WK is regular U-Joints front and rear, but the WK/XK also has a wheelbase that supports a long rear driveshaft.

    High Pinion? What is the longevity and reliability of those? I suspect it takes more design, development and testing to make sure you get everything right to keep the higher pinion well lubricated, BUT I'm Guessing. If I guess right, that may be a factor for an OEM, that has to warranty the axles, and knows they have a customer base that expects the Axle NOT to fail during its life, despite them ignoring and neglecting the prescribed maintenance.
     
  14. unverferth

    unverferth Well-Known Member

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    Speaking here of Bob. How is he doing these days ?
     
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  15. Dr. Jeep

    Dr. Jeep Well-Known Member

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    Lubrication isn't an issue. High pinion front D30's and D44's have been used in the JK since '07.

    The issue is the ring gear. In a high pinion design the ring gear is reverse cut from the standard ring gear. Apples to apples, this reduces the strength of the ring gear by roughly a quarter. This is why they are primarily used in front axle applications, and when used in rearends, you see the high pinion application as a modified Dana 60, for the much larger ring gear.

    Dana can make a high pinion rear axle with a 44 centersection, but they would have to do something about the strength of the ring gear to put it in the JL application.
     
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  16. Dr. Jeep

    Dr. Jeep Well-Known Member

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    ...and let me just say that a JL with a high pinion rear 44 with a gearset having something approaching the strength of a D60 high pinion gearset, but not the diameter of a 60 ring gear... would be awesome. If it's possible.
     
  17. Rick Anderson

    Rick Anderson Well-Known Member

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    The ZF 8spd lower ratios might allow a lower numeric axle ratio (taller axle ratio) that usually provides a little more strength. BUT, I'm almost positive the increase of strength is in the pinion gear, it does nothing to change the ring gear. So it really doesn't help, I see your point, the high pinion may be impractical for the JL because of ring gear strength.
     
  18. Ruptured Duck

    Ruptured Duck Active Member

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    No, sorry, the images show what earlier Wranglers looked like (OE slip yoke) not later JK's. I was just trying to give everyone an image for what was being discussed.
     
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  19. Dr. Jeep

    Dr. Jeep Well-Known Member

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    Now there is a way to gain the strength back (and more) of a reverse cut ring gear, and that is by cryogenically freezing the gearset. But of course for a mass produced axle this is almost certainly cost-impractical.
     
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  20. Rick Anderson

    Rick Anderson Well-Known Member

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    Now that I have thought about it, I think I can see why a low pinion has more strength than a high pinion. Going forward, in a low pinion the teeth of the pinion gear push off the inclined plane of the teeth on the ring gear, i.e. it pushes the ring gear in the direction of rotation. But going forward, in a high pinion the teeth of the pinion gear grab and pull on the teeth of the ring gear, it pulls the ring gear in the directions of rotation.

    Another way to say it, low pinion going forward the pinion gear pushes the ring gear teeth into the ring gear, while a high pinion going forward the pinion gear pulls the ring gear teeth away from the ring gear.
     

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