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4l80e no forth or overdrive

Discussion in 'Mechanic and Repair' started by JCLawn and more, Oct 20, 2013.

  1. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Messages: 5,281

    So my 93 1 ton with a 4l80e will not go into forth or overdrive. When I bought it a week ago it would go into both when the trans got to 175 then it would go out. All I had to do is flick the key and get it back. Once it got to 180 it would not come back. Now after a long drive it won't come back at all. Any thoughts? If someone says just rebuilt it ill slap you........
  2. tigerepairdotcom

    tigerepairdotcom LawnSite Senior Member
    Messages: 330

    Do we know the history? Was it rebuild is it unknown? How many miles

    There are plenty things that could've gone wrong with the transmission. I have seen TC not pulling failed seal or a missing ball in the intermediate plate.
    Not much to advice but pull the tranny open it up and try to find what is wrong.

    Suggest also doing a fluid pressure test.
  3. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Messages: 5,281

    Ya were dropping the pan and cleaning all the valves, checking o-rings. The torque converter does not slip. I've been searching for hrs in this thing.
    Posted via Mobile Device
  4. DSLS

    DSLS LawnSite Member
    Messages: 59

    There is a map sensor and mass air flow near the throttle body make sure both are good - check vacuum line and connections also could be solenoids in transmission. Should be a diagram of vacuum line on sticker near radiator. Any of these should cause codes to come up when scanned. Did the fluid seemed to be burnt looking or smelling? If no codes come up then may very well be clutch packs and have to be rebuilt. Start with a scan of codes first to diagnose it something as simple as a bad sensor under the hood, vacuum line, out of adjustment linkage, or wire connection can cause this.
  5. JCLawn and more

    JCLawn and more LawnSite Fanatic
    from MI
    Messages: 5,281

    :laugh::laugh::laugh::laugh::laugh: I should explained its a 6.5 diesel. I have no mass air flow, no throttle body, and no vacuum lines. That's right no vacuum lines :clapping: I think I have the cat in the bag on this one so Ill explain how this sucker works for future people. I throw codes for my tcc(torque converter controler) also called the PWM(pulse with modulation) (that took and hr to figure out it was the same thing). Also it threw the variable force motor or if your looking for the part its called valve pressure control solenoid. Also it threw the 2-3 shift solenoid. Mind you all my problems are temp related.

    So when trans temp gets to 180 I loose torque lockup and then 4th a bit later. If I flick the key I got this back until I do this like 5 times and then it will stay off. I thought I lost them completely but I found out to day if I disconnect the battery and reset everything I get it back. Today we dropped the pan and changed the filter and it took to 190 before I lost torque and lockup. Here is what I think is wrong even though we are replacing all the parts listed above and the trans temp sensor. Well first off ill say that 1 gear and 3rd are shifted by a solenoid and 2 is limp mode default and 4th is shifted into by a valve also the same with torque lock up. So I think what is causing this is the valve pressure control solenoid which half worked and when the oil gets so thin it loses pressure. It will shift from 1-3 because second is forced and 1 and 3rd are done by solenoids. 4th will only work if the 2-3 solenoid gets enough pressure. So its throwing the 2-3 solenoid and tcc codes because when the fluid is hot it can't create enough pressure and thus can't stay in torque or 4th. We are replacing the temp sensor because if it goes bad it will read -40 and will only stay in third.

    Did ya get all that? :hammerhead::hammerhead:

    This was extremely helpful to us http://helpwrench.com/forums/showthread.php?210-GM-4L80E-4L80-E-Transmission-rebuild-guide-amp-pictures-1 No site was a one stop shop for my questions.

    This pdf was helpful for crossing GM lingo with Aftermarket lingo http://www.automaticchoice.com/Catalogue/4l80e.pdf
    Last edited: Oct 21, 2013

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