Smoked the power transfer unit



ChryslerMiniVan.net is the premier Chrysler Minivan Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 10 of 20

Thread: Smoked the power transfer unit

  1. #1
    Join Date
    Mar 2010
    Posts
    61
    Thanks
    0
    Thanked 2 Times in 2 Posts


    Smoked the power transfer unit

    I need to replace the Power Transfer unit on my 2000 awd van.
    Has anyone done this yet? If so do you have any advice to offer before I just dive in and start taking stuff apart?
    I still need to relocate a replacement unit as well. Any advice would be welcomed.

  2. Remove Advertisements
    Chrysler Minivan Forums
    Advertisements

  3. #2
    Join Date
    May 2010
    Location
    Central Connecticut
    Posts
    115


    Can't help with replacement but for parts you might try here Car Parts
    2000 T&C Limited 3.8L AWD
    1979 MGB Dual Carb 1.8L

  4. #3
    Join Date
    May 2010
    Posts
    72
    Thanks
    0
    Thanked 13 Times in 12 Posts


    Quote Originally Posted by gmule View Post
    I need to replace the Power Transfer unit on my 2000 awd van.
    Has anyone done this yet? If so do you have any advice to offer before I just dive in and start taking stuff apart?
    I still need to relocate a replacement unit as well. Any advice would be welcomed.
    Removing and replacing the PTU is fairly straightforward. Be sure to have new, properly-sized axle seals installed or it will leak.

    Any idea about what caused the failure? The PTU is a simple gear unit and usually not prone to having problems.

    The viscous coupling unit, however, which is forward-mounted between the PTU and the rear drive shaft, can suffer problems when it sees excessive slippage usually due to running tires of different sizes front and rear. This would be easier to change than the PTU.

    Hope this helps.

  5. Remove Advertisements
    Chrysler Minivan Forums
    Advertisements

  6. #4
    Join Date
    Mar 2010
    Posts
    61
    Thanks
    0
    Thanked 2 Times in 2 Posts


    My wife was driving the van when she called me telling me that the van would no longer move forward. It would however back up. I decided to pull the torque tube between the PTU and viscous coupler. After that I was able to drive the van home. There is still some light chatering coming from the area around the PTU. I am not 100% sure that the PTU is broken but that is where I intend to start looking for broken pieces. If I can remove the unit I can examine it and go from there to see what the problem may be. I also learned that the PTU lubricant is seperate from the transmission. I am certain that the fluid in the PTU has never been changed in 180K and as far as I know the unit could be dry or very low causing the unit to fail from lack of lubrication.

  7. #5
    Join Date
    May 2010
    Posts
    72
    Thanks
    0
    Thanked 13 Times in 12 Posts


    Yes, the PTU uses heavy (90wt) gear oil.

    In addition to the viscous coupler (forward end of the drive shaft), there is also an overrunning clutch with a reverse lock-up (rear end of the drive shaft).

    Here's a good explanation of the system from the Allpar site:

    There seems to be some confusion on how the AWD minivans works. I have a 1997 AWD Grand Caravan and have recently replaced the driveshaft and serviced the rear differential and over running clutch. The viscous coupling is mounted on the forward end of the drive shaft. All power directed to the rear axle runs through the viscous coupling and there is no clutch that either bypasses it or locks it up.
    Just forward of the rear differential mounted between the driveshaft and the differential pinion is a unit with an overunning clutch and a dog clutch. When in any forward gear the dog clutch is disengaged. Whenever the front wheels are the same speed or slower than the rear wheels the over running clutch is slipping and no torque is supplied to the rear wheels. Whenever the front wheels are faster than the rear, as when they slip on ice or snow, the over running clutch locks up transferring torque to the rear axle, but only as much as the viscous coupling will supply. When the front axle is only slightly faster than the rear, only a small amount of torque is transferred. When in reverse the dog clutch engages which locks the driveshaft to the rear differential pinion because the over running clutch function is backwards for driving the van in reverse.
    ...
    The AWD system does not split torque unevenly left to right. The left and right half shafts have a normal differential identical in function, if not truly identical, to the FWD differential. The driveshaft to the rear is turned by a ring and pinion driven directly from the ring gear (actually a helical gear) of the front axle differential. The ring gear drives the pinion, unlike normal ring and pinions where the pinion drives the ring. This whole ring gear assembly is hollow so that the a shaft from the front axle differential to the right side front axle half shaft can pass through the ring gear without affecting or being affected by power to the rear axle. There are no limited slip differentials in the transaxle.
    If the PTU was locking up with the rear drive shaft in place, I would think it would still do so with the rear drive shaft removed. You may want to check out the universal joints too.

    Good luck and please let us know what you find.

  8. #6
    Join Date
    Mar 2010
    Posts
    61
    Thanks
    0
    Thanked 2 Times in 2 Posts


    HMMMMM, that gives me more questions. If the viscous coupler was bad would it cause binding while turning? she was turning into a parking space when this happened.

  9. #7
    Join Date
    May 2010
    Posts
    72
    Thanks
    0
    Thanked 13 Times in 12 Posts


    Quote Originally Posted by gmule View Post
    HMMMMM, that gives me more questions. If the viscous coupler was bad would it cause binding while turning? she was turning into a parking space when this happened.
    I think it's possible since the wheels are rotating at different speeds while turning. The viscous coupler is the thing that fails most often with these AWD vans. Usually it's because people put unmatched snow tires on the front. A small difference in tire circumference (front to back) causes rapid heat build-up in the viscous coupler and they will fail. Hopefully that's it because it's the cheapest part to replace...you could even find a used one.

    I think it's a great system all in all...better traction than my Jeeps and 4wd truck.

  10. #8
    Join Date
    Mar 2010
    Posts
    61
    Thanks
    0
    Thanked 2 Times in 2 Posts


    Do you know how to diagnose this?

  11. #9
    Join Date
    May 2010
    Posts
    72
    Thanks
    0
    Thanked 13 Times in 12 Posts


    I would first check to see if the viscous coupler slips just using hand force. I would also try to get ahold of a new one to compare it with. If yours feels like it is seized but the new one slips, I'd say you have your answer.

    As far as I know they are not servicable.

  12. #10
    Join Date
    Mar 2010
    Posts
    61
    Thanks
    0
    Thanked 2 Times in 2 Posts


    Ok I'll give that try

    Thanks for the help

+ Reply to Thread

Quick Reply Quick Reply

Bookmarks

Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts