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Thread: Jakes Performance 4L80E Stage III tuning

  1. #1
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    Default Jakes Performance 4L80E Stage III tuning

    If anyone isn't familiar with this transmission it is built to handle 1000 crank HP. Its a fully automatic and has trans brake capabilities in D1-D3. I have not messed with transmission tuning yet. I just got the 408 running good. The first forward 1-2 shift is nice and soft. Every 1-2 shift after that is hard. Even with the lightest throttle applied. 2-3 is medium and 3-4 is medium under light throttle. Under heavy throttle they all hit hard just like a shift kit worked over transmission should. I wish the trans would 1-2 shift all the time like 2-3 does or 3-4 under light throttle. It does great on the first shift of starting the car. After that it hit hard. My line pressure under throttle is 190-200. The converter locks up like it should and overall I am happy with everything. How can we make light throttle shifting 1-2 softer, but retain the firm shift under heavy throttle? Why does it shift good then shift hard after the first shift? I am reading line pressure from a hose and gauge coming off the transmission. It also seems to shift softer when its cold. After the fluid warms up it shifts harder.

  2. #2
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by redtacoma31 View Post
    If anyone isn't familiar with this transmission it is built to handle 1000 crank HP. Its a fully automatic and has trans brake capabilities in D1-D3. I have not messed with transmission tuning yet. I just got the 408 running good. The first forward 1-2 shift is nice and soft. Every 1-2 shift after that is hard. Even with the lightest throttle applied. 2-3 is medium and 3-4 is medium under light throttle. Under heavy throttle they all hit hard just like a shift kit worked over transmission should. I wish the trans would 1-2 shift all the time like 2-3 does or 3-4 under light throttle. It does great on the first shift of starting the car. After that it hit hard. My line pressure under throttle is 190-200. The converter locks up like it should and overall I am happy with everything. How can we make light throttle shifting 1-2 softer, but retain the firm shift under heavy throttle? Why does it shift good then shift hard after the first shift? I am reading line pressure from a hose and gauge coming off the transmission. It also seems to shift softer when its cold. After the fluid warms up it shifts harder.
    You're saying that this happens even though line pressure is good...?

    If line pressure is high during the soft shift, there might be an internal leak;

    the ECM/tune is behaving correctly in commanding higher pressure in correlation with high throttle/load.


    This is the key ("shift softer when its cold")... this points to internal/hydraulic issue.

  3. #3
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    Joecar this happens with forward line pressure of 190-200. The transmission shift from 1-2 the very first time is soft. Every other 1-2 shift after that while driving on the same key cycle is aggressive. The transmission has different cold fluid parameters right? When I say cold I am meaning the 30 degrees it starts off at. When the weather was warmer and I was driving it while it was 80 outside it shifted hard after the first 1-2 shift.

    Where would an internal leak be?

    Why would it shift different on the very first shift?

  4. #4
    Joe (Moderator) joecar's Avatar
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    Yes, the tune has temperature/pressure adjust tables... but you said line pressure was 190-200 psi during the soft shifts.


    Post your tune file, let's take a look at it.

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