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A670 harsh engage into D

Discussion in 'Repairs, Maintenance, Help' started by Kevin1990, May 31, 2020.

  1. Kevin1990

    Kevin1990 Active Member

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    Gent's...

    I bought a neglected 1st gen Voyager, 3.0 / 31th.

    The trans fluid is brownish worn, N to D is brutal, really.

    Anything to know for adjusting the bands for a worn out unit?

    I bought this dump well overpriced, not gonna put a trans in there. So i try to save it with new fluid and a correct service.

    Thankful for any advice,
    Kevin
     
  2. AllanC

    AllanC Well-Known Member

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    By the title of your thread I will assume that you get harsh engagement when you move the transmission selector into Drive range. Since the vehicle is not moving that would bring first gear into usage. Service manual for a 1988 minivan with 3 speed automatic transaxle mated to the 3.0 liter V6 indicates engine idle speed too high or transmission valve body malfunction or leakage as a cause. In first gear the rear clutch and overrunning clutch elements are utilized.
     
  3. GLHS60

    GLHS60 Well-Known Member

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    Anything you do to service the trans will probably make engagement harsher.

    Often the differential is worn and is the cause of the harsh clunk.

    There is considerable play between the axle and spider gears and the housing and cross pin.

    Normal wear is no issue but the cross pin is often excessively worn and can fall out.

    This results in a catastrophic failure with a broken trans case.

    Minivans suffered this fate more than cars especially in winter/icy climates.

    Chrysler added diff pin retainer clips around 2001 to prevent the pin falling out.

    The pin its self is retained by a tiny roll pin that is easily snapped off.

    When the roll pin snaps there is nothing retaining the diff pin so it can drop out.

    Thanks
    Randy

    Chrysler part # 04800059AA
    [​IMG]
     
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  4. ImperialCrown

    ImperialCrown Moderator
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    A worn or loose front motor mount can also cause a harsh clunk when put into gear.
    You can try a filter and fluid change. Band adjustment is probably OK.
     
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  5. GLHS60

    GLHS60 Well-Known Member

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    Very good point, hopefully that's his issue.

    Diff pin busted cases seem less frequent now.

    Were there ever very many in your area??

    Thanks
    Randy
    .


     
  6. AllanC

    AllanC Well-Known Member

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    I thought the failure of the differential spider gear pin was limited to the 40/41TE 4 speed automatic transaxles. The A413 / A670 / 31TH 3 speed transaxles did not have this issue.
     
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  7. KOG

    KOG KOG

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    He has a 670, not a 604.
     
  8. GLHS60

    GLHS60 Well-Known Member

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    4 speeds in minivans certainly were the worst offenders..

    All shared the same roll pin/shaft issues.

    Thanks
    Randy
     
  9. Kevin1990

    Kevin1990 Active Member

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    I still have a diff and those bat wings stored new. But i think this assembly is 604 trans only.

    The 3spd transmissions also had that problem, but i never worked on one of them before.

    Bad thing is, first generation Minivans are extremely rare over here. I have never spotted one in traffic, never...
     
  10. AC TC

    AC TC Well-Known Member

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    Check for slop in driveshaft, engine mounts and front end bushings besides adjusting the bands.
     
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  11. ImperialCrown

    ImperialCrown Moderator
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    I had seen sheared differential case roll pins mostly on minivans and heavier cars (greatest weight) with the 3.3L/3.8L engines (greatest torque).
    The worst offender was getting stuck in a snow bank and spinning the tires. With one tire spinning and one tire sitting still, this would be the greatest stress for a differential. Some owners would violently rock the vehicle D to R to try to get unstuck.
    ATF isn't a great differential lube to begin with (too thin) and the spider gear would seize to the diff shaft, twist it and shear the roll pin. This usually sent the shaft through the case and the vehicle was then totally immobilized.
    In about 2002, the roll pin was eliminated and the diff shaft was allowed to 'float' and turn (as necessary) in the diff case. The 'case saver brackets' held the shaft in position.
     
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  12. AllanC

    AllanC Well-Known Member

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    One definitive way to differentiate the 3 speed automatic transaxle from the 4 speed transaxle is to look at the outline of the oil pan. See attached image.

    Transmission Pans  3 speed  4 speed.gif
     
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  13. Kevin1990

    Kevin1990 Active Member

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    Sooo...

    Did a fluid and filter change and replaced the lower motor mount. Definatly better, but it revs / slips for a moment when shifting into 3rd.

    Adjustment or probably an internal leak?
     
  14. ImperialCrown

    ImperialCrown Moderator
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    If the shift points are too early, it will slip into the next upshift.
    I believe that the 3.0L has a rod between the throttle body lever and the kickdown lever. Lengthening it will give later shifts. Shortening it will give earlier shifts. The rod should be free to 'flop around' with light spring pressure back towards the idle position.
     
  15. GLHS60

    GLHS60 Well-Known Member

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    Exactly as above..., but...if still soggy..

    I've refreshed many A 413's with Ford ATF as it firms up the shifts noticeably.

    Most disagree so please don't bash my findings as they are my own.

    Same goes for most non electronic transmissions, electronic require specific fluid.

    Specific as to constant temperature viscosity not more or less, they need it constant.

    Most older non electronic auto trans appreciate a bump in viscosity.

    I also use a viscosity enhancer but don't post it due to criticism.

    Hopefully a TV linkage adjustment helps, I consider it a fine tuning tool.

    Factory settings are average and can be altered to suit conditions.

    Thanks
    Randy
     
  16. chuzz

    chuzz Well-Known Member

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    I knew a lot of the guys back in the days of my youth that ran the type F fluid in their 904's and 727's for "crisper" shifts. Bottom line is, though, that if you have worn clutches, you're just putting off the inevitable rebuild.
     
  17. ImperialCrown

    ImperialCrown Moderator
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    Yep, the old racers used Type-F in Torqueflites as it was a 'gritty' fluid compared to Dexron and helped at launch. It probably will shorten clutch life in applications that it isn't intended for.
    On the 2-3 upshift, the kickdown band is released and the front clutch is engaged. Front clutch may be worn or have low apply pressure if it slips into 3rd (direct) gear?
     

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