4l80e hard shift from 2-3 gear.

Discussion in 'Transmissions' started by Mildphil, Jul 24, 2019.

  1. Mildphil

    Mildphil I'm Awesome

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    If it comes down to replacing the valve body I'll do it. Hopefully the reverse boost valve fixes my issue. Either way, anything is better than having a trans shop charge me an arm an a leg to perform a swap-nosis.
     
  2. Mildphil

    Mildphil I'm Awesome

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    Also, I'm assuming the correct reverse boost valve is the first one (3420001k)? That was the one in the sonnax article Andy linked.

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  3. MIHELA

    MIHELA King of the Scrapyard

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    The piston is under that big can looking thing next to the valve body. The 3420001K is the valve I used on my trans.
     
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  4. Mildphil

    Mildphil I'm Awesome

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    Yeah the can looking thing with a few bolts holding it right? Did you happen to have an issue similar to me?
     
  5. MIHELA

    MIHELA King of the Scrapyard

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    I rebuilt my trans straight from the junkyard. The 95 trans is much less likely to break that piston, however I did have a broken accumulator spring. That could cause a harder shift and would be another thing you could look for. Valve body has to come out for that however.
     
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  6. Mildphil

    Mildphil I'm Awesome

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    Just ordered the sonnax piece first to see if that works. How mich did it cost to rebuild a junkyard unit? The thought has crossed my mind a few times in the past just in case if mine ever died.
     
  7. Mildphil

    Mildphil I'm Awesome

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    Boost valve came in, I'll install it once the rain subsides and update the thread with the results.

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  8. Mildphil

    Mildphil I'm Awesome

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    Ok so I'm a little confused here. The kit has a small aluminum balance disc that is supposed to be inserted from the TOP of the pump, where as the rest of the kit (sleeve and valve) go in at the BOTTOM. Is there any way to insert the piece from the bottom? Is the piece absolutely necessary? The sonnax instructions online are kind of lacking.

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  9. andy396

    andy396 I'm Awesome

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    I guess it depends on the condition of the old plug. I’m not sure exactly which part is to blame for the leakage that causes high line pressure. I guess worse case you don’t replace it and the problem still remains and you have to then pull the trans.
     
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  10. Mildphil

    Mildphil I'm Awesome

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    Yeah I couldn't think of any way to get that plug in without ripping out the pump, so I just did the valve. Time will tell how it goes. I have noticed though that after dropping the pan and replacing with fresh fluid each time, the 3rd gear shift has gotten more tame. It's more of a firm shift than a harsh thud that makes all the interior plastic creak. I also noticed that around sharper turns, it shifts into 3rd butter smooth, very weird. The harsh shift in general doesn't seem to be as consistent. I'll keep the thread updated on how it drives with the valve and sleeve in.

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