allison mh4000 trans

Discussion in 'Class A / Diesel Pushers' started by rhall, Sep 19, 2009.

  1. rhall

    rhall New Member

    i have a monaco signature with a 525 cummins and a mh4000 trans. my eng. temp runs no more than 203 degrees but trans temp runs about 235 is ok
     
  2. dbarton291

    dbarton291 Senior Member

    RE: allison mh4000 trans

    I assume you are reading a gauge on the dash. At what point in the system does this gauge get its reading? If it's in the line going to the cooler, you're okay.

    If you're suspicious the gauge may be inaccurate, you can always have someone put a manual gauge in the to cooler circuit and compare the two, or use a good laser thermometer.
     
  3. rhall

    rhall New Member

    Re: allison mh4000 trans

    the gauge on the dash reads off the cooler line , the reading on the panasonic screen reads off the sump i am told my monaco.
     
  4. dbarton291

    dbarton291 Senior Member

    Re: allison mh4000 trans

    There's a to cooler and from cooler. It's kind of important to know which one the gauge reads from.

    What reading were you referring to in your original question? Was that the gauge or the screen?
     
  5. rhall

    rhall New Member

    Re: allison mh4000 trans

    the screen in the original question, i think it is to the cooler, if looking at the rear of trans. it is on the right side and runs to the top of the tank and the other line goes to the bottom.thanks randy
     
  6. dbarton291

    dbarton291 Senior Member

    Re: allison mh4000 trans

    To cooler is on the left. If the gauge sending unit is in the hose on the right, it's reading temperature after the oil has already passed through the cooler.

    If the screen is reading the sump temperature, the sump typically runs about 200. Maximum intermittent sump temp is 250.
     
  7. LEN

    LEN Senior Member

    Re: allison mh4000 trans

    Hey dbarton291,
    No problem here with the trans, but just a big thank you from all of us/me. I really enjoy reading(sorry others problems) and learning. Your knowledge base is great, please keep up the good work.

    LEN
     
  8. dbarton291

    dbarton291 Senior Member

    Re: allison mh4000 trans

    Glad to help. Keeps me outta the tavern and the pool hall.
     
  9. rhall

    rhall New Member

    Re: allison mh4000 trans

    hi dbarton291 , thanks for the info. would there be another way to check the sump temp. other than the screen. i have a laser temp gun. thanks randy
     
  10. dbarton291

    dbarton291 Senior Member

    Re: allison mh4000 trans

    I'd be more concerned about getting the gauge so it's showing the "to cooler" temp, which is the hottest point in the transmission oil system.

    But as to your question, the screen is probably reporting sump temp off the J1939 CAN link, which is a reading from the thermistor in the sump.

    The sump is pretty thick. Using the laser gun pointed at the sump will show you the temp of the outside of the sump, but not necessarily the oil in it. The laser gun can sometimes be used on fittings that have a temp sender in them to compare the temp of the fitting to the temp displayed on the gauge.

    Your temp gauge is in the from cooler line. That oil goes directly into the sump and should closely correspond to sump temp. Do the gauge and the screen show different readings? How about the laser gun at the spot where the temp sender is?
     
  11. rhall

    rhall New Member

    Re: allison mh4000 trans

    the laser at the temp sender reads about 35 to 40 degrees diff. than the gauge on the dash. iam going to replace that gauge.i am going to check the temp at the sender and temp on the screen today and will let you know . thanks randy
     
  12. rhall

    rhall New Member

    Re: allison mh4000 trans

    i drove the mh about 50 miles today .i drove it at about 85 mph up and down some hills the temp on the monitor showed 227 when i stopped and checked the to cooler line at the trans it was 187 the temp at the from cooler line at the trans were the sender is it showed 204 with the laser do you think it will be ok . can the sump j1939 link be wrong
     
  13. dbarton291

    dbarton291 Senior Member

    Re: allison mh4000 trans

    The temperatures you're quoting don't indicate a problem in and of themselves. What makes no sense is you're reading the from cooler higher than the to cooler, and the sump is higher than both.

    I can believe the J1939 CAN signal for sump temp that goes to the screen might have something throwing it off, but the to cooler oil being cooler than the oil that has passed through the cooler is unusual.

    I double checked the hose locations. To cooler is the left port as looking at the rear of the trans. From cooler is on the right. Your plumbing makes sense for a side tank cooler(side tank attached to the engine radiator). The to cooler goes in the bottom of the tank, which pushes any air out as the oil flows in. The from cooler comes from the top of the tank back to the trans.

    If this vehicle were mine, I'd put some manual gauges in both those cooler ports and get some very accurate readings of what's going on there. If the to cooler oil really is cooler than the from cooler oil, that would mean the engine water is hotter than the trans oil and is actually heating the trans oil. But "heating" it to 204 degrees is still well below the max temp for the trans. However, that still leaves the question of why the sump is hotter than both unanswered.

    I assume, because you haven't mentioned it, there's no output retarder on the transmission and you don't see any foaming of the oil on the dipstick.

    Another thing I'd do if it were mine is put a temperature probe for a manual gauge in a fitting that adapts to the drain plug hole. That would verify what the sump temperature actually is. I'd be surprised if the sump really is hotter than both the to and from cooler oil.

    You may not want to go to all that trouble or expense because the temperature values you are quoting do not indicate temperatures that are over any published maximum.
     
  14. rhall

    rhall New Member

    Re: allison mh4000 trans

    i did not understand why the temp was lower at the to cooler than the from cooler line either. but i will put a manual gauge in the pan to see what it reads. thanks alot for your input randy
     

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