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Thread: 4L80E Full Throttle Shift Issue

  1. #1

    Default 4L80E Full Throttle Shift Issue

    This is a new build that I just got running. It shifts just fine part throttle, but will not shift under full throttle. Part throttle goes up & down through the gears with no issues, including OD & TCC lock and unlock. Full throttle it seems like the computer is commanding the shift, but the transmission does not come out of 1st, and it hits the rev limiter. Once I back off it will go ahead & shift.

    The details of the build are:
    55 Chevy 210
    6.0 LQ9
    2004 4L80E
    Holley Dominator ECU
    Borg S480 turbo
    3.55 gears in the 9"
    28" tall Hoosier quick time pro tires

    Am I reading the datalog correctly? It is commanding the shift where it shows 2nd gear right? The shift point set at 6400, but the RPM never drops and it quickly hits the rev limiter at 7K. Speed when it hits the limiter is 59 MPH, so with my gearing that's telling me it is not getting out of 1st gear, even though the log shows the trans should be in 2nd.


  2. #2

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    Try changing your TPS scale to a max of 96%. I had issues with missing shift points by several hundred RPM, and that fixed it.

  3. #3

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    Thanks, I'll give that a shot.

  4. #4

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    I'm having a similar problem, how do I change the TPS scale?

  5. #5

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    Click on the little Holley computer icon at the top then select sensor/scale, TPS. I've also been told that the shift solenoids in the 4L80E are sluggish, and may require some playing around with shift points & rev limiter to dial them in. I've noticed this in my car as well.

  6. #6

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    My transmission guy told me to play with the WOT shift points as well. He said to lower them and see if it starts working, then work back up. I'm also going to put a pressure transducer in, to monitor the actual line pressure and see what it's doing. The weather has been too crappy to test anything yet though.
    Last edited by squarles67; 01-18-2017 at 12:34 PM.

  7. #7

    Default 4L80E Shift Issues

    What did you ever figure out with you shift points? I'm having a similar problem. I have the Dominator with the 4L80E harness and ever since I got the car running it has always had transmission issues like smoking 2nd and 3rd gear. Now it’s happened again. This is a twin turbo car and I was having issues making more that 6 psi boost. We finally found the MAP sensor was bad. It would only make 6 psi of boost at the turbo air ports. We noticed the PSIA was reading 15 right where the boost controller was telling it to go. I pulled my transmission and sure enough 2nd and 3rd smoked again. My transmission builder told me that maybe the bad MAP sensor could be making the transmission act funny by not allowing enough pressure during the hard acceleration. Any thoughts on what I can look at? When I monitor the transmission psi it reads 0% when it shifts from 1st to 2nd.
    Last edited by Greychevelle; 07-02-2019 at 01:30 PM.

  8. #8

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    It turned out to be a bad seal between the filter and the case. Just driving around the seal was below the fluid level, under full throttle it would uncover and suck air. Put a pressure transducer in and started monitoring pressure, it didn't drop to zero, but you could really see a difference. Ended up having to rebuild the trans as the direct and intermediate clutches were smoked.
    Last edited by squarles67; 07-03-2019 at 01:24 PM.

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