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Thread: Caravan PTU info

  1. #1
    Garrett booster
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    Caravan PTU info

    Does anyone know the differences from the original PTU and the 02-04 carvan PTU? I know the pacifica differences.

  2. #2
    turbo addict
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    Re: Caravan PTU info

    Following. I got those pictures for you. I am also curious on this as the Pacifica PTU raises the driveshaft output up quite a bit while the van one seems to lower it. I like the design of the Pacifica one better, but I'm unsure how well it will actually fit, though I do intend on trying it before I put my '90 back together since the K-frame is out and everything is easy access currently.

    One thing that bugs me is how fast the driveshaft will be spinning at high speed. Both the van and the Pacifica have ~3.3 gear ratios (they are different, NOT interchangeable from what I know about these systems unless you don't care about frying the VC), so the shaft is spinning its @ss off. Other than that, they are both super stout units when compared to DSM and 3S stuff.

  3. #3
    Garrett booster
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    Re: Caravan PTU info

    From what I gathered the older PTU is 3.4166 and the rear is 3.45. I have no info on the newer 02+ ratios if there any different. I plan to run a different rear diff any way, IRS 9" has a 3.40 option so the gear ratio will be a lot closer. I want the VC gone and the awd system to be locked.

  4. #4

    Re: Caravan PTU info

    I am far from an expert on this, but doesn't your change to the rear ratio effect the bias (front or rear) of the system? (ie make it rear biased?) Do you expect any issues with bind because of the removal of the VC?

    Are you intending this to be a drag only setup?

  5. #5
    Garrett booster
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    Re: Caravan PTU info

    Eliminating the VC and running the oem gear there will be a slight bind. Everyone I've talked to says it's not enough to cause any problems. But I rather get it as close as possible, so 3.40 with IRS 9" rear to 3.4166 isn't anything. All out drag setup, cant have front spinning and then rear grabbing.

  6. #6
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    Re: Caravan PTU info

    Quote Originally Posted by c2xejk View Post
    I am far from an expert on this, but doesn't your change to the rear ratio effect the bias (front or rear) of the system? (ie make it rear biased?) Do you expect any issues with bind because of the removal of the VC?

    Are you intending this to be a drag only setup?
    The reason for the different gear ratios front to back is due to the VC. In order to ensure that the VC will act as quickly as possible, it must always be in a slight state of slip (a few %). The front is always overdriven compared to the rear for both stability and quick system activation.

    I want to keep the VC due to my goals of road course activities, so I have been researching ways to rebuild it, modify it, etc. It *can* be done, but I'm unsure if the parts like seals can be obtained. I would figure with enough looking it should be possible. You can achieve up to ~98% lock with a VC (still not as efficient as a totally locked driveline, obviously).

  7. #7
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    Re: Caravan PTU info

    Yea I wouldn’t recommend what I want to do for a street car that’s driven a lot.

  8. #8
    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: Caravan PTU info

    So uhh, what are the pacifica differences?

    Dont push the red button.You hear me?

  9. #9
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    Re: Caravan PTU info

    Quote Originally Posted by Vigo View Post
    So uhh, what are the pacifica differences?
    The Pacifica PTU is a different design and places the output shaft above the centerline of the FD diff in the transmission. The van PTU places the output shaft lower than the centerline of the FD diff.

    The Pacifica PTU goes though a transfer shaft to turn the output pinion whereas the van one drives it directly off of the PTU input shaft that goes into the FD diff.

    The Pacifica PTU is basically flat on the "engine" side of the case and does not protrude any farther than the adapter plate, so there is no engine block interference. The van PTU has a big lump that sticks out because of the way the pinion is driven that can cause block and pan interference necessitating grinding of the block and or the PTU case.

    The Pacifica unit is physically larger, and so are the gears in "meatiness" (both have drive ring gears that are ~6.5"). It *appears* stronger IMHO and certainly has a courser tooth pitch.

    The van drive ring gear can be unbolted from the input shaft, so theoretically it would be *fairly* simple to make a custom gearset for it. The Pacifica one appears to be 1 piece and would require a lot more work to make a custom ratio simply because the transfer gear has to be included on the shaft.

    If you want pictures I can send them to you. PM me.

  10. #10
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: Caravan PTU info

    Quote Originally Posted by Reaper1 View Post
    The Pacifica PTU is a different design and places the output shaft above the centerline of the FD diff in the transmission. The van PTU places the output shaft lower than the centerline of the FD diff.

    The Pacifica PTU goes though a transfer shaft to turn the output pinion whereas the van one drives it directly off of the PTU input shaft that goes into the FD diff.

    The Pacifica PTU is basically flat on the "engine" side of the case and does not protrude any farther than the adapter plate, so there is no engine block interference. The van PTU has a big lump that sticks out because of the way the pinion is driven that can cause block and pan interference necessitating grinding of the block and or the PTU case.

    The Pacifica unit is physically larger, and so are the gears in "meatiness" (both have drive ring gears that are ~6.5"). It *appears* stronger IMHO and certainly has a courser tooth pitch.

    The van drive ring gear can be unbolted from the input shaft, so theoretically it would be *fairly* simple to make a custom gearset for it. The Pacifica one appears to be 1 piece and would require a lot more work to make a custom ratio simply because the transfer gear has to be included on the shaft.

    If you want pictures I can send them to you. PM me.
    Chris, would it be too much trouble to post pics here?
    I'd like to see them, even though I probably would never get to do that project. It sounds interesting for sure.

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    Wayne H.

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  11. #11
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    Re: Caravan PTU info

    Quote Originally Posted by wheming View Post
    Chris, would it be too much trouble to post pics here?
    I'd like to see them, even though I probably would never get to do that project. It sounds interesting for sure.

    Sent from my ONEPLUS A6000 using Tapatalk
    I will see if I can get them to post up. It's one of the reasons I just emailed them to Vigo. I just noticed my subscription ran out, too...gotta renew!

  12. #12
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: Caravan PTU info

    Quote Originally Posted by Reaper1 View Post
    I will see if I can get them to post up. It's one of the reasons I just emailed them to Vigo. I just noticed my subscription ran out, too...gotta renew!
    If you messenger them to me I'll post them.
    I find it super easy using Tapatalk for the forum.

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    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
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    '89 Dodge Caravan SE 2.5L turbo auto, "Mean Mini" yes, Gus' Mean Mini! (Current best 11.7786@113.04 mph! - Jan 15th, 2017 Fayetteville Dragway, NC)
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  13. #13
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: Caravan PTU info

    Sorry, I forgot to post these from Chris.

    Van PTU


    Sent from my ONEPLUS A6000 using Tapatalk
    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
    '05 PT GT 2.4T HO autostick
    '89 Plymouth Acclaim 2.5L turbo auto, "Slugmobile" yes, THE Slugmobile!
    '89 Dodge Caravan SE 2.5L turbo auto, "Mean Mini" yes, Gus' Mean Mini! (Current best 11.7786@113.04 mph! - Jan 15th, 2017 Fayetteville Dragway, NC)
    MeanMini dragracing videos: https://www.youtube.com/playlist?lis...URZLB1RxGYF6vw
    and other cars, trucks and motorcycles
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  14. #14
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: Caravan PTU info

    Pacifica PTU

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    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
    '05 PT GT 2.4T HO autostick
    '89 Plymouth Acclaim 2.5L turbo auto, "Slugmobile" yes, THE Slugmobile!
    '89 Dodge Caravan SE 2.5L turbo auto, "Mean Mini" yes, Gus' Mean Mini! (Current best 11.7786@113.04 mph! - Jan 15th, 2017 Fayetteville Dragway, NC)
    MeanMini dragracing videos: https://www.youtube.com/playlist?lis...URZLB1RxGYF6vw
    and other cars, trucks and motorcycles
    https://www.youtube.com/user/SlugmobileMeanMini

  15. #15
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    Re: Caravan PTU info

    Thanks for posting those, Wayne!

  16. #16
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: Caravan PTU info

    Quote Originally Posted by Reaper1 View Post
    Thanks for posting those, Wayne!
    No problem!

    Sent from my ONEPLUS A6000 using Tapatalk
    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
    '05 PT GT 2.4T HO autostick
    '89 Plymouth Acclaim 2.5L turbo auto, "Slugmobile" yes, THE Slugmobile!
    '89 Dodge Caravan SE 2.5L turbo auto, "Mean Mini" yes, Gus' Mean Mini! (Current best 11.7786@113.04 mph! - Jan 15th, 2017 Fayetteville Dragway, NC)
    MeanMini dragracing videos: https://www.youtube.com/playlist?lis...URZLB1RxGYF6vw
    and other cars, trucks and motorcycles
    https://www.youtube.com/user/SlugmobileMeanMini

  17. #17
    Garrett booster
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    Re: Caravan PTU info

    Caravan PTU would be my choice

  18. #18
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    Re: Caravan PTU info

    Quote Originally Posted by boots View Post
    Caravan PTU would be my choice
    For what reasons? Just curious. I know there's certain aspects to it that are desirable, but that case interference thing is very close to a deal-breaker.

    An interesting note is that years ago I found that there was replacement gears available for the van PTU. Dunno if they are still around.

  19. #19
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    Re: Caravan PTU info

    Well as anything, I always think ahead of me breaking it. The caravan PTU design is a lot simpler, and making a billet bevel gear will be easier. Also making another case is option. What clearance issues are you talking about?

  20. #20
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    Re: Caravan PTU info

    Because of the position of the ring gear being on the input shaft, the case protrudes past the adapter plate/bearing carrier of the transmission. This causes interference with the oil pan rail on the engine and part of the block if it's a 2.2/2.5 or a 3.0 V6. Grinding can clearance things, but I'm not too big of a fan of that solution as I'm unsure about the compromise to any strength of the parts by doing this. I'm sure for low power stuff and soft launches it'll be fine, but start abusing things...well...who knows? For this reason, that is why I like the Pacifica unit. I just recently found out that the newer Jeep Cherokee PTU is designed in a similar way, but it includes electronically controlled hi/low ranges. According to this video it's 2.92:1 instead of the 3.xx:1 of the van and Pacifica https://www.offroadxtreme.com/featur...e-14-cherokee/

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