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tropical36's avatar
tropical36
Explorer
Jun 16, 2013

Transmission Problem?

Climbed over the southern Rockies in extreme heat the other day on I8 and in to San Diego. Tranny overheated and went in to fail safe on that long eastern climb, even though the engine temp was OK or unless my gauge isn't reading correctly. Anyway after disconnecting the toad and a little cool down, we proceeded on our way with seemingly no ill effects. Next morning and in now habitable daytime temperatures, my shift lever felt tight in movement, but then quickly loosened up to normal after a few miles. Next morning, same thing and I did need and added some fluid, thinking that was the problem. Following morning, same thing and hope to know more as I proceed up the CA coast.
Anybody ever had this happen or might have some idea of why this is occuring? I have lubed everything I can see and feel that this is possibly an internal problem with the transmission. Not a big deal so far, but why?
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  • Jim's avatar
    Jim
    Explorer
    Jun 17, 2013
    Dave seems to be offline at the moment. From what I've heard and read here on the forum, yeah, disconnecting the battery ground for 15 minutes will probably reset the memory. I don't think this is one of those problems that has a reset procedure for the tranni but you might check your service manual for that first.
  • tropical36's avatar
    tropical36
    Explorer
    Jun 17, 2013
    Daveinet wrote:
    A couple of things happen in fail safe mode. The ECM runs the pump pressure wide open to prevent slip. That also increase the TC lockup pressure to max, to prevent slip. Once this happens, the ECM remembers this condition and maybe assuming that the pump pressure needs to be operated higher from now on. If that is the case, it should eventually figure out everything is OK and go back to normal. I would change the fluid (especially if it smells burnt), maybe reset the ECM, and see if things settle down. I realize you are out on the trip, but I think it is worth it, to change the fluid.

    Here is a couple of articles that tell you a little about how it works, and how the ECM is programed to think:
    http://www.motor.com/article.asp?article_ID=1039
    http://forum.efilive.com/showthread.php?4305-4L80E-Reference-Material

    Great info and a good tech explanation. The fluid looks good and smells good, but new can't hurt or can it, as I've heard of problems with changing, unless it's always been done regularly and I have no history on this rig that we bought in 07? As for resetting the ECM, I thought that as soon as I began to read your excellent post. Now, what is the best way to do that and can I just disconnect the chassis battery for a few minutes to accomplish the same thing?
  • Daveinet's avatar
    Daveinet
    Explorer
    Jun 17, 2013
    A couple of things happen in fail safe mode. The ECM runs the pump pressure wide open to prevent slip. That also increase the TC lockup pressure to max, to prevent slip. Once this happens, the ECM remembers this condition and maybe assuming that the pump pressure needs to be operated higher from now on. If that is the case, it should eventually figure out everything is OK and go back to normal. I would change the fluid (especially if it smells burnt), maybe reset the ECM, and see if things settle down. I realize you are out on the trip, but I think it is worth it, to change the fluid.

    Here is a couple of articles that tell you a little about how it works, and how the ECM is programed to think:
    http://www.motor.com/article.asp?article_ID=1039
    http://forum.efilive.com/showthread.php?4305-4L80E-Reference-Material

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