97 Ram 1500 -no engagement

Discussion in 'Transmission Forum' started by alaska viking, Oct 19, 2016.

  1. billr

    billr wrench Staff Member

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    I, too, am reluctant to believe a sprag could be so temperature-sensitive. I still feel a check of line-pressure could be worthwhile to evaluate all this "from the outside".
     
  2. kev2

    kev2 wrench

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    Some info I hope could help
     

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  3. bp042665

    bp042665 hunting nut

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    the line pressure is controled by the computer on this year by the transducer and pressure sensor thats where live data comes in if the commanded and actual are the same them you have internal problem
     
  4. kev2

    kev2 wrench

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    the PCM controls line pressure SO are we back to what are the codes? Or a definite 'hard' failure - I am an optimist -always . Its not dead yet:)
     
  5. billr

    billr wrench Staff Member

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    Oh, for sure, response from the OP is needed about thorough scanning and codes is needed! I would also like the OP to confirm that the "manual" posted by kev2 applies to the trans in question; that it at least looks like what is in the manual. There is a lot of valuable info in that manual, but I hate to wade into it very deep if it doesn't apply.
     
  6. nickb2

    nickb2 Wrench. I help when I can

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    Just for information, if the PCM controls the line pressure, why then does the manual say that the throttle and line pressure are adjustable?

    I know there is a pressure solenoid/sensor for the governor.

    Something is eluding me here.

    I remember a few guys back in the day backing off a full turn to drop line pressure on these dodge rams and similar products.

    I know my question is not related to the thread, but if BP says it's PCM controlled, then I am now confused.

    I see no mention of a transducer on this model. Line and throttle adjustements are made at valve body.

    Could it be that my french is getting in the way and what we call a pressure sensor is what you guy,s down south call a transducer?
     
  7. nickb2

    nickb2 Wrench. I help when I can

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    Well, I did a google research, and yes the pressure sensor is also called a transducer. Who knew?

     
  8. billr

    billr wrench Staff Member

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    Just to keep you confused... a PCM can control LP even without a sensor/transducer, but it will be "open loop" and less accurate.
     
  9. nickb2

    nickb2 Wrench. I help when I can

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    Ok, someone is joshing me around. Or my head is full of salt.

    From my understanding, a LP pressure sensor/tranducer is a hall effect or a pulse width modulated type deal.

    Now I am talking out of my arse. How can that go into open loop and still read actual line pressure??
     
    Last edited: Oct 31, 2016
  10. nickb2

    nickb2 Wrench. I help when I can

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    So to confuse me further, I know for a fact that chrysler/mopar introduced a variable line fluid pressure sensor not so long ago and yes it is PCM controlled (introduce caps here) VIA THE INPUT AND OUTPUT SPEED SENSORS.

    End of caps.

    So in essence, we are no longer reading actual fluid pressure, but trying to reduce clutch slippage by reading throttle angle and in essence, using a open loop format for the VFS to obtain desired pressure line.


    http://www.allpar.com/mopar/transmissions/variable-line-pressure.html
     
  11. nickb2

    nickb2 Wrench. I help when I can

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    So, since this is a 1997 dodge ram, did the TCM of that era have the ability to read that algorythm. ??

    So, with the 3 speed I don't see that happening. Only with the 4 speed E series.

    Damn, my head is hurting right now. I need a refresher course pronto.
     
  12. billr

    billr wrench Staff Member

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    No, I am not joking you. Does anybody object to our having hijacked this thread, should Nickb2 and I take this to PM or the Lounge?

    Pressure transducers are usually based on piezo-resistance now. Neither PWM or Hall-effect are involved are involved in reading LP (Hall could be, but I have never heard of a pressure transducer using Hall-effect). Control of pressure, yeah, that is often accomplished by PWM of a valve spool/poppet.

    I mis-spoke a bit: without a transducer, control of the LP is "open loop", but control of the trans operation can be (and usually is) "closed loop". "Closed" or "open" depends on how you define the control loop being discussed...
     
  13. nickb2

    nickb2 Wrench. I help when I can

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    Actually, ùi do this often.
     
  14. nickb2

    nickb2 Wrench. I help when I can

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    funny

     

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