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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
    turbo addict
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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
    Garrett booster
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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.

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